Amazon EC2 FAQs

Amazon Elastic Compute Cloud (Amazon EC2) is a web service that provides resizable compute capacity in the cloud. It is designed to make web-scale computing easier for developers.

Q: What can I do with Amazon EC2?

Just as Amazon Simple Storage Service (Amazon S3) enables storage in the cloud, Amazon EC2 enables “compute” in the cloud. Amazon EC2’s simple web service interface allows you to obtain and configure capacity with minimal friction. It provides you with complete control of your computing resources and lets you run on Amazon’s proven computing environment. Amazon EC2 reduces the time required to obtain and boot new server instances to minutes, allowing you to quickly scale capacity, both up and down, as your computing requirements change. Amazon EC2 changes the economics of computing by allowing you to pay only for capacity that you actually use.

Q: How can I get started with Amazon EC2?

To sign up for Amazon EC2, click the “Sign up for This Web Service” button on the Amazon EC2 detail page. You must have an Amazon Web Services account to access this service; if you do not already have one, you will be prompted to create one when you begin the Amazon EC2 sign-up process. After signing up, please refer to the Amazon EC2 documentation, which includes our Getting Started Guide.

Q: Why am I asked to verify my phone number when signing up for Amazon EC2

Amazon EC2 registration requires you to have a valid phone number and email address on file with AWS in case we ever need to contact you. Verifying your phone number takes only a couple of minutes and involves receiving a phone call during the registration process and entering a PIN number using the phone key pad.

Q: What can developers now do that they could not before?

Until now, small developers did not have the capital to acquire massive compute resources and insure they had the capacity they needed to handle unexpected spikes in load. Amazon EC2 enables any developer to leverage Amazon’s own benefits of massive scale with no up-front investment or performance compromises. Developers are now free to innovate knowing that no matter how successful their businesses become, it will be inexpensive and simple to ensure they have the compute capacity they need to meet their business requirements.

The “Elastic” nature of the service allows developers to instantly scale to meet spikes in traffic or demand. When computing requirements unexpectedly change (up or down), Amazon EC2 can instantly respond, meaning that developers have the ability to control how many resources are in use at any given point in time. In contrast, traditional hosting services generally provide a fixed number of resources for a fixed amount of time, meaning that users have a limited ability to easily respond when their usage is rapidly changing, unpredictable, or is known to experience large peaks at various intervals.

Q: How do I run systems in the Amazon EC2 environment?

Once you have set up your account and select or create your AMIs, you are ready to boot your instance. You can start your AMI on any number of On-Demand Instances by calling the RunInstances API. You simply need to state how many instances you wish to start. If you wish to run more than 20 On-Demand Instances, complete the Amazon EC2 instance request form.

If Amazon EC2 is able to fulfill your request, RunInstances will return success, and we will start setting up your instances. You can check on the status of your instances using the DescribeInstances API call. You can also programmatically terminate any number of your instances using the TerminateInstances API call.

If you have a running instance using an Amazon EBS boot partition, you can also call the StopInstances API to release the compute resources but preserve the data on the boot partition. You can call the StartInstances API when you are ready to restart the associated instance with the Amazon EBS boot partition.

In addition, you have the option to use Spot Instances to reduce your computing costs when you have flexibility in when your applications can run. Read more about Spot Instances for a more detailed explanation on how Spot Instances work.

If you prefer, you can also perform all these actions from the AWS Management Console or through the command line using our command line tools, which have been implemented with this web service API.

Q: What is the difference between using the local instance store and Amazon Elastic Block storage (Amazon EBS) for the root device?

When you launch your Amazon EC2 instances you have the ability to store your root device data on Amazon EBS or the local instance store. By using Amazon EBS, data on the root device will persist independently from the lifetime of the instance. This enables you to stop and restart the instance at a subsequent time, which similar to shutting down your laptop and restarting it when you need it again.

Alternatively, the local instance store only persists during the life of the instance. This is an inexpensive way to launch instances where data is not stored to the root device. For example, some customers use this option to run large web sites where each instance is a clone to handle web traffic.

Q: How quickly will systems be running?

It typically takes less than 10 minutes from the issue of the RunInstances call to the point where all requested instances begin their boot sequences. This time is dependant on a number of factors including: the size of your AMI, the number of instances you are launching, and how recently you have launched that AMI. Images launched for the first time may take slightly longer to boot.

Q: How do I load and store my systems with Amazon EC2?

Amazon EC2 allows you to set up and configure everything about your instances from your operating system up to your applications. An Amazon Machine Image (AMI) is simply a packaged-up environment that includes all the necessary bits to set up and boot your instance. Your AMIs are your unit of deployment. You might have just one AMI or you might compose your system out of several building block AMIs (e.g., webservers, appservers, and databases). Amazon EC2 provides a number of tools to make creating an AMI easy. Once you create a custom AMI, you will need to bundle it. If you are bundling an image with a root device backed by Amazon EBS, you can simply use the bundle command in the AWS Management Console. If you are bundling an image with a boot partition on the instance store, then you will need to use the AMI Tools to upload it to Amazon S3. Amazon EC2 uses Amazon EBS and Amazon S3 to provide reliable, scalable storage of your AMIs so that we can boot them when you ask us to do so.

Or, if you want, you don’t have to set up your own AMI from scratch. You can choose from a number of globally available AMIs that provide useful instances. For example, if you just want a simple Linux server, you can choose one of the standard Linux distribution AMIs.

Q: How do I access my systems?

The RunInstances call that initiates execution of your application stack will return a set of DNS names, one for each system that is being booted. This name can be used to access the system exactly as you would if it were in your own data center. You own that machine while your operating system stack is executing on it.

Q: Is Amazon EC2 used in conjunction with Amazon S3?

Yes, Amazon EC2 is used jointly with Amazon Simple Storage Service (Amazon S3) for instances with root devices backed by local instance storage. By using Amazon S3, developers have access to the same highly scalable, reliable, fast, inexpensive data storage infrastructure that Amazon uses to run its own global network of web sites. In order to execute systems in the Amazon EC2 environment, developers use the tools provided to load their Amazon Machine Images (AMIs) into Amazon S3 and to move them between Amazon S3 and Amazon EC2. See "How do I load and store my systems with Amazon EC2?" for more information about AMIs.

We expect developers to find the combination of Amazon EC2 and Amazon S3 to be very useful. Amazon EC2 provides cheap, scalable compute in the cloud while Amazon S3 allows users to store their data reliably.

Q: How many instances can I run in Amazon EC2?

You are limited to running 20 On-Demand or Reserved Instances and running 100 Spot Instances per region. If you need more instances, complete the Amazon EC2 instance request form and your use case and instance increase will be considered. Limit increases are tied to the region they were requested for.

Q: Are there any limitations in sending email from EC2 instances?

Yes. In order to maintain the quality of EC2 addresses for sending email, we enforce default limits on the amount of email that can be sent from EC2 accounts. If you wish to send larger amounts of email from EC2, you can apply to have these limits removed from your account by filling out this form.

Q: How quickly can I scale my capacity both up and down?

Amazon EC2 provides a truly elastic computing environment. Amazon EC2 enables you to increase or decrease capacity within minutes, not hours or days. You can commission one, hundreds or even thousands of server instances simultaneously. When you need more instances, you simply call RunInstances, and Amazon EC2 will typically set up your new instances in a matter of minutes. Of course, because this is all controlled with web service APIs, your application can automatically scale itself up and down depending on its needs.

Q: What operating system environments are supported?

Amazon EC2 currently supports a variety of operating systems including: RedHat Linux, Windows Server, openSuSE Linux, Fedora, Debian, OpenSolaris, Cent OS, Gentoo Linux, and Oracle Linux. We are looking for ways to expand it to other platforms in future releases.

Q: How is this service different than a plain hosting service?

Traditional hosting services generally provide a pre-configured resource for a fixed amount of time and at a predetermined cost. Amazon EC2 differs fundamentally in the flexibility, control and significant cost savings it offers developers, allowing them to treat Amazon EC2 as their own personal data center with the benefit of Amazon.com’s robust infrastructure.

When computing requirements unexpectedly change (up or down), Amazon EC2 can instantly respond, meaning that developers have the ability to control how many resources are in use at any given point in time. In contrast, traditional hosting services generally provide a fixed number of resources for a fixed amount of time, meaning that users have a limited ability to easily respond when their usage is rapidly changing, unpredictable, or is known to experience large peaks at various intervals.

Secondly, many hosting services don’t provide full control over the compute resources being provided. Using Amazon EC2, developers can choose not only to initiate or shut down instances at any time, they can completely customize the configuration of their instances to suit their needs – and change it at any time. Most hosting services cater more towards groups of users with similar system requirements, and so offer limited ability to change these.

Finally, with Amazon EC2, developers enjoy the benefit of paying only for their actual resource consumption – and at very low rates. Most hosting services require users to pay a fixed, up-front fee irrespective of their actual computing power used, and so users risk overbuying resources to compensate for the inability to quickly scale up resources within a short time frame.

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Billing

Q: How will I be charged and billed for my use of Amazon EC2?

You pay only for what you use and there is no minimum fee. Pricing is per instance-hour consumed for each instance type. Partial instance-hours consumed are billed as full hours. There is no Data Transfer charge between two Amazon Web Services within the same region (i.e. between Amazon EC2 US West and another AWS service in the US West). Data transferred between AWS services in different regions will be charged as Internet Data Transfer on both sides of the transfer. Usage for other Amazon Web Services is billed separately from Amazon EC2.

For EC2 pricing information, please visit the pricing section on the EC2 detail page.

Q: When does billing of my Amazon EC2 systems begin and end?

Billing commences when Amazon EC2 initiates the boot sequence of an AMI instance. Billing ends when the instance terminates, which could occur through a web services command, by running “shutdown -h”, or through instance failure.

Q: What defines billable EC2 instance-hours?

Instance-hours are billed for any time your instances are in a “running” state. If you no longer wish to be charged for your instance, you must terminate it to avoid being billed for additional instance-hours.

Q: If I have two instances in different availability zones, how will I be charged for regional data transfer?

Each instance is charged for its data in and data out. Therefore, if data is transferred between these two instances, it is charged out for the first instance and in for the second instance.

Q. If I have two instances in different regions, how will I be charged for data transfer?

Each instance is charged for its data in and data out at Internet Data Transfer rates. Therefore, if data is transferred between these two instances, it is charged at Internet Data Transfer Out for the first instance and at Internet Data Transfer In for the second instance.

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Hardware Information

Q: What kind of hardware will my application stack run on?

Your application will execute on a virtual computer that we call an instance. You have the choice of several instance types, allowing you to select a configuration of memory, CPU, and instance storage that is optimal for your application:

Standard Instances
Instances of this family are well suited for most applications.
Small Instance (Default)

1.7 GB of memory, 1 EC2 Compute Unit (1 virtual core with 1 EC2 Compute Unit), 160 GB of local instance storage, 32-bit platform

Large Instance

7.5 GB of memory, 4 EC2 Compute Units (2 virtual cores with 2 EC2 Compute Units each), 850 GB of local instance storage, 64-bit platform

Extra Large Instance

15 GB of memory, 8 EC2 Compute Units (4 virtual cores with 2 EC2 Compute Units each), 1690 GB of local instance storage, 64-bit platform

High-Memory Instances

Instances of this family offer large memory sizes for high throughput applications, including database and memory caching applications.
High-Memory Double Extra Large Instance

34.2 GB of memory, 13 EC2 Compute Units (4 virtual cores with 3.25 EC2 Compute Units each), 850 GB of local instance storage, 64-bit platform

High-Memory Quadruple Extra Large Instance

68.4 GB of memory, 26 EC2 Compute Units (8 virtual cores with 3.25 EC2 Compute Units each), 1690 GB of local instance storage, 64-bit platform

High-CPU Instances

Instances of this family have proportionally more CPU resources than memory (RAM) and are well suited for compute-intensive applications.
High-CPU Medium Instance

1.7 GB of memory, 5 EC2 Compute Units (2 virtual cores with 2.5 EC2 Compute Units each), 350 GB of local instance storage, 32-bit platform

High-CPU Extra Large Instance

7 GB of memory, 20 EC2 Compute Units (8 virtual cores with 2.5 EC2 Compute Units each), 1690 GB of local instance storage, 64-bit platform

Cluster Compute Instances

Instances of this family provide proportionally high CPU with increased networking performance and are well suited for High Performance Compute (HPC) applications and other demanding network-bound applications. Learn more about use of this instance type for HPC applications.
Cluster Compute Quadruple Extra Large Instance

23 GB of memory, 33.5 EC2 Compute Units, 1690 GB of local instance storage, 64-bit platform, 10 Gigabit Ethernet

See Amazon EC2 Instance Types for details on available configurations. You have full and exclusive access to an instance once you have commissioned it.

Q: How do I select the right instance type?

Amazon EC2 instances are grouped into four families: Standard, High-Memory, High-CPU, and Cluster Compute. Standard Instances have memory to CPU ratios suitable for most general purpose applications; High-Memory instances offer larger memory sizes for high throughput applications, including database and memory caching applications; and High-CPU instances have proportionally more CPU resources than memory (RAM) and are well suited for compute-intensive applications. Cluster Compute instances provide a very large amount of CPU coupled with a high performance network making them well suited for High Performance Compute (HPC) applications and other demanding network-bound applications. When choosing instance types, you should consider the characteristics of your application with regards to resource utilization and select the optimal instance family and size.

For most applications, the standard instance types are appropriate. These include the Small Instance (m1.small), Large Instance (m1.large), and Extra Large Instance (m1.xlarge). For high throughput applications, such as database and memory caching applications, the High-Memory instances are well suited. These are the High-Memory Double Extra Large Instance (m2.2xlarge) and the High-Memory Quadruple Extra Large Instance (m2.4xlarge). For compute-intensive applications such as rendering, search indexing, and computational analysis, the High-CPU Instances are well suited. The High-CPU instance types are the High-CPU Medium Instance (c1.medium) and the High-CPU Extra Large Instance (c1.xlarge). For HPC and other network-bound applications such as computational biology and chemistry, engineering design and simulation, and financial analytics, the Cluster Compute Quadruple Extra Large Instance (cc1.4xlarge) is well suited. For details, please see Amazon EC2 Instance Types.

One of the advantages of EC2 is that you pay by the instance hour, which makes it convenient and inexpensive to test the performance of your application on different instance families and types. One good way to determine the most appropriate instance family and instance type is to launch test instances and benchmark your application.

Q: What is a “EC2 Compute Unit” and why did you introduce it?

Transitioning to a utility computing model fundamentally changes how developers have been trained to think about CPU resources. Instead of purchasing or leasing a particular processor to use for several months or years, you are renting capacity by the hour. Because Amazon EC2 is built on commodity hardware, over time there may be several different types of physical hardware underlying EC2 instances. Our goal is to provide a consistent amount of CPU capacity no matter what the actual underlying hardware.

Amazon EC2 uses a variety of measures to provide each instance with a consistent and predictable amount of CPU capacity. In order to make it easy for developers to compare CPU capacity between different instance types, we have defined an Amazon EC2 Compute Unit. The amount of CPU that is allocated to a particular instance is expressed in terms of these EC2 Compute Units. We use several benchmarks and tests to manage the consistency and predictability of the performance from an EC2 Compute Unit. One EC2 Compute Unit provides the equivalent CPU capacity of a 1.0-1.2 GHz 2007 Opteron or 2007 Xeon processor. This is also the equivalent to an early-2006 1.7 GHz Xeon processor referenced in our original documentation. Over time, we may add or substitute measures that go into the definition of an EC2 Compute Unit, if we find metrics that will give you a clearer picture of compute capacity.

See Amazon EC2 Instance Types for additional details.

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Security

Q: How do I prevent other people from viewing my systems?

You have complete control over the visibility of your systems. The Amazon EC2 security systems allow you to place your running instances into arbitrary groups of your choice. Using the web services interface, you can then specify which groups may communicate with which other groups, and also which IP subnets on the Internet may talk to which groups. This allows you to control access to your instances in our highly dynamic environment. Of course, you should also secure your instance as you would any other Linux host.

Q: Where can I find more information about security on AWS?

For more information on security on AWS please refer to our Amazon Web Services: Overview of Security Processes document and to our Amazon EC2 running Windows Security Guide.

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Elastic IP

Q: Why am I limited to 5 Elastic IP addresses per region?

Public (IPV4) internet addresses are a scarce resource. There is only a limited amount of public IP space available, and Amazon EC2 is committed to helping use that space efficiently.

By default, all accounts are limited to 5 Elastic IP addresses per region. If you need more the 5 Elastic IP addresses, we ask that you apply for your limit to be raised. We will ask you to think through your use case and help us understand your need for additional addresses. You can apply for more Elastic IP address here. Any increases will be specific to the region they have been requested for.

Q: Why am I charged when my Elastic IP address is not associated with an instance?

In order to help ensure our customers are efficiently using the Elastic IP addresses, we impose the $.01/hr charge for each address when it is not mapped to an instance.

Q: Do I need one Elastic IP address for every instance that I have running?

No. You do not need an Elastic IP address for all your instances. By default, every instance comes with a private IP address and an internet routable public IP address. These addresses are fixed for the life of the instance. These IP addresses should be adequate for many applications where you do not need a long lived internet routable end point. Compute clusters, web crawling, and backend services are all examples of applications that typically do not require Elastic IP addresses.

Q: How long does it take to remap an Elastic IP address?

The remap process currently takes several minutes from when you instruct us to remap the Elastic IP until it fully propagates through our system.

Q: Can I configure the reverse DNS record for my Elastic IP address?

Yes, you can configure the reverse DNS record of your Elastic IP address by filling out this form. Note that a corresponding forward DNS record pointing to that Elastic IP address must exist before we can create the reverse DNS record.

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Availability Zones

Q: How isolated are Availability Zones from one another?

Each availability zone runs on its own physically distinct, independent infrastructure, and is engineered to be highly reliable. Common points of failures like generators and cooling equipment are not shared across Availability Zones. Additionally, they are physically separate, such that even extremely uncommon disasters such as fires, tornados or flooding would only affect a single Availability Zone.

Q: Is Amazon EC2 running in more than one region? When will EC2 be expanding to new regions?

Yes, EC2 is running in four regions, each of which has multiple Availability Zones. The regions are US East (Northern Virginia), US West (Northern California), EU (Ireland), and Asia Pacific (Singapore).

Q: How can I make sure that I am in the same Availability Zone as another developer?

We do not currently support the ability to coordinate launches into the same Availability Zone across AWS developer accounts.

Q: If I transfer data between availability zones using public IP addresses, will I be charged twice for Regional Data Transfer (once because it’s across zones, and a second time because I’m using public IP addresses)?

No. Regional Data Transfer rates apply if at least one of the following is true, but is only charged once for a given instance even if both are true:

The other instance is in a different availability zone, regardless of which type of address is used.
Public or Elastic IP addresses are used, regardless of which zone the other instance is in.

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Amazon Elastic Block Storage (EBS)

Q: What happens to my data when a system terminates?

The data stored on a local instance store will persist only as long as that instance is alive. However, data that is stored on an Amazon EBS volume will persist independently of the life of the instance.

Therefore, we recommend that you should use the local instance store for temporary data and if you want to increase your data durability we recommend using Amazon EBS volumes or backing up the data to Amazon S3.

Q: What kind of latency and throughput rates can I expect to see from Amazon EBS volumes?

The latency from an Amazon EC2 instance to an Amazon EBS volume is similar to the latency you would see from the local Amazon EC2 instance storage drive. I/O rates can vary significantly based on the size of the requests, the randomness of the access patterns, and the caching strategy used by the application. As such, the most accurate measure is to benchmark your specific application on an Amazon EBS volume.

Q: Do you plan to support multiple instances accessing a single volume?

While you are able to attach multiple volumes to a single instance, attaching multiple instances to one volume is not supported at this time.

Q: Will I be able to access my snapshots using the regular Amazon S3 APIs?

No, snapshots are only available through the Amazon EC2 APIs.

Q: Do volumes need to be un-mounted in order to take a snapshot? Does the snapshot need to complete before the volume can be used again?

No, snapshots can be done in real time while the volume is attached and in use. However, snapshots only capture data that has been written to your Amazon EBS volume, which might exclude any data that has been locally cached by your application or OS. In order to ensure consistent snapshots on volumes attached to an instance, we recommend cleanly detaching the volume, issuing the snapshot command, and then reattaching the volume. For Amazon EBS volumes that serve as root devices, we recommend shutting down the machine to take a clean snapshot.

Q: Are snapshots versioned? Can I read an older snapshot to do a point-in-time recovery?

Each snapshot is given a unique identifier, and customers can create volumes based on any of their existing snapshots.

Q: Do you offer encryption on Amazon EBS volumes or snapshots?

No. If encryption is important to you, we recommend that you run an encrypted file system on top of your Amazon EBS volume.

Q: What charges apply when using Amazon EBS shared snapshots?

If you share a snapshot, you won’t be charged when other users make a copy of your snapshot. If you make a copy of another user’s shared volume, you will be charged normal EBS rates.

Q: Can users of my Amazon EBS shared snapshots change any of my data?

Users who have permission to create volumes based on your shared snapshots will first make a copy of the snapshot into their account. Users can modify their own copies of the data, but the data on your original snapshot and any other volumes created by other users from your original snapshot will remain unmodified.

Q: How can I discover Amazon EBS snapshots that have been shared with me?

You can find snapshots that have been shared with you by selecting “Private Snapshots” from the viewing dropdown in the Snapshots section of the AWS Management Console. This section will list both snapshots you own and snapshots that have been shared with you.

Q: How can I find what Amazon EBS snapshots are shared globally?

You can find snapshots that have been shared globally by selecting “Public Snapshots” from the viewing dropdown in the Snapshots section of the AWS Management Console.

Q: How can I find a list of Amazon Public Data Sets?

All information on Public Data Sets is available in our Public Data Sets Resource Center. You can also obtain a listing of Public Data Sets within the AWS Management Console by choosing “Amazon Snapshots” from the viewing dropdown in the Snapshots section.

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Amazon CloudWatch

Q: What is the minimum time interval granularity for the data that Amazon CloudWatch receives and aggregates?

Metrics are received and aggregated at 1 minute intervals.

Q: Which operating systems does Amazon CloudWatch support?

Amazon CloudWatch receives and provides metrics for all Amazon EC2 instances and should work with any operating system currently supported by the Amazon EC2 service.

Q: Will I lose the metrics data if I disable monitoring for an Amazon EC2 instance?

You can retrieve metrics data for any Amazon EC2 instance up to 2 weeks from the time you started to monitor it. After 2 weeks, metrics data for an Amazon EC2 instance will not be available if monitoring was disabled for that Amazon EC2 instance. If you want to archive metrics beyond 2 weeks you can do so by calling mon-get-stats command from the command line and storing the results in Amazon S3 or Amazon SimpleDB.

Q: Can I access the metrics data for a terminated Amazon EC2 instance or a deleted Elastic Load Balancer?

Yes. Amazon CloudWatch stores metrics for terminated Amazon EC2 instances or deleted Elastic Load Balancers for 2 weeks.

Q: Does the Amazon CloudWatch monitoring charge change depending on which type of Amazon EC2 instance I monitor?

No, the Amazon CloudWatch monitoring charge does not vary by Amazon EC2 instance type.

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Auto Scaling

Q: Can I scale up my Amazon EC2 capacity fast but scale it down slowly?

Yes. For example, you can define a scale up condition to increase your Amazon EC2 capacity by 10% and a scale down condition to decrease it by 5%.

Q: How does Auto Scaling decide which Amazon EC2 instance in the Auto Scaling Group to terminate when the scaling condition is met?

Auto Scaling will randomly pick and terminate any Amazon EC2 instance from your Auto Scaling Group if the scaling condition is met.

Q: What happens if a scaling activity causes me to reach my Amazon EC2 limit of instances?

Auto Scaling Service cannot scale past the Amazon EC2 limit of instances that you can run. If you need more Amazon EC2 instances, complete the Amazon EC2 instance request form.

Q: What happens to my Amazon EC2 instances if I delete my Auto Scaling Group?

Auto Scaling will not allow you to delete your Auto Scaling Group if it contains running Amazon EC2 instances. You have to empty the Auto Scaling Group by setting its size to 0 using the as-set-desired-capacity command from the command line. You can safely delete your Auto Scaling Group once it is empty.

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Elastic Load Balancing

Q: Which operating systems does Elastic Load Balancing support?

Elastic Load Balancing supports Amazon EC2 instances with any operating system currently supported by the Amazon EC2 service.

Q: Which protocols does Elastic Load Balancing support?

Elastic Load Balancing supports load balancing of applications using HTTP and TCP protocols.

Q: Can I use a single Elastic Load Balancer for handling HTTP and HTTPS requests?

Yes, you can map the HTTP port 80 and HTTPS port 443 to a single Elastic Load Balancer.

Q: How many connections will my load balanced Amazon EC2 instances need to accept from the Elastic Load Balancer?

Elastic Load Balancer does not cap the number of connections that it can attempt to establish with your load balanced Amazon EC2 instances. You can expect this number to scale with the number of concurrent HTTP requests (for HTTP routing) or the number of concurrent TCP connections (for TCP routing) that the Elastic Load Balancer receives.

Q: Can I load balance Amazon EC2 instances launched using a Paid AMI?

Not at this time. Manually registering a Paid AMI based Amazon EC2 instance with the Elastic Load Balancer or using a Paid AMI with an Auto Scaling Group that is associated with the Elastic Load Balancer is not supported. Elastic Load Balancing with Paid AMI support will be available soon.

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Reserved Instances

Q: What is a Reserved Instance?

Reserved Instances give you the option to make a low, one-time payment for each instance you want to reserve and in turn receive a significant discount on the hourly usage charge for that instance. After the one-time payment for an instance, that instance is reserved for you, and you have no further obligation; you may choose to run that instance for the discounted usage rate for the duration of your term, or if and when you do not use the instance, you will not pay usage charges on it.

Q: How is a Reserved Instance different than an On-Demand Instance?

Functionally, Reserved Instances and On-Demand Instances are exactly the same. They are launched and terminated in the same way, and they function identically once running. This makes it easy for you to seamlessly use both Reserved and On-Demand Instances without making any changes to your code. The only difference is that with a Reserved Instance, you pay a low, one-time payment and receive a lower usage rate to run the instance than with an On-Demand Instance.

Q: How do I purchase and start up a Reserved Instance?

You can purchase Reserved Instances through the AWS Management Console or using EC2 API tools. In the AWS Management Console, simply click the “Reserved Instances” button in the EC2 Instances section, and select “Purchase Reserved Instances”. The wizard will walk you through the purchase.

Using the API tools, you can list the available Reserved Instances for purchase with the DescribeReservedInstancesOfferings API method. You can then purchase an EC2 Reserved Instance by calling the PurchaseReservedInstancesOffering method.

Launching a Reserved Instance is no different than launching an On-Demand Instance. You simply use the RunInstances command or launch an instance via the AWS Management Console. Amazon EC2 will optimally apply the cheapest rate that you are eligible for in the background.

Q: How do I control which instances are billed at the Reserved Instance rate?

The RunInstances command does not distinguish between On-Demand and Reserved Instances. When computing your bill, our system will automatically optimize which instances are charged at the lower Reserved Instance rate to ensure you always pay the lowest amount.

Q: How many Reserved Instances can I purchase?

You can purchase as few as 1 or as many as 20 Reserved Instances per Availability Zone each month with the EC2 APIs. If you need additional Reserved Instances, complete the form found here.

Q: Can a Reserved Instance that I’ve bought for a particular instance type (i.e. High-CPU Extra Large Instance) be applied to a different instance type that I am running (i.e. Standard Large Instance)?

No. Each Reserved Instance is associated with a specific instance type, and can only be applied to that instance type for the duration of the Reserved Instance term.

Q: Can I move a Reserved Instance from one Region or Availability Zone to another?

No. Each Reserved Instance is associated with a specific Region and Availability Zone, which is fixed for the lifetime of the Reserved Instance and cannot be changed.

Q: Do I need to specify an Availability Zone when I launch my instances in order to take advantage of my Reserved Instances?

Yes. When you purchase a Reserved Instance you specify the Availability Zone in which you want to reserve that instance. In order to use that Reserved Instance, you need to ensure that you launch your instance in that same Availability Zone. Additionally, you can purchase a Reserved Instance in an Availability Zone where you already have a running instance, and the Reserved Instance will automatically get applied to that existing instance.

Q: Can I cancel a Reserved Instance?

The one-time payment for a Reserved Instances is not refundable. However, you can choose not to run or entirely stop using your Reserved Instance at any time, at which point you will not incur any further usage charges.

Q: When are Reserved Instances activated?

A Reserved Instance is activated once your one-time payment has successfully been authorized. You can follow the status of your Reserved Instance on the AWS Account Activity page.

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Spot Instances

Q. What is a Spot Instance?

Spot Instances are a new way to purchase and consume Amazon EC2 Instances. They allow customers to bid on unused EC2 capacity and run those instances for as long as their bid exceeds the current Spot Price. The Spot Price changes periodically based on supply and demand, and customers whose bids meet or exceed it gain access to the available Spot Instances. Spot Instances are complementary to On-Demand Instances and Reserved Instances, providing another option for obtaining compute capacity.

Q. How is a Spot Instance different than an On-Demand Instance or Reserved Instance?

Spot Instances provide the ability for customers to purchase compute capacity with no upfront commitment, at hourly rates usually lower than the On-Demand rate. Spot Instances allow you to specify the maximum hourly price that you are willing to pay to run a particular instance type. Amazon EC2 sets a Spot Price for each instance type in each region, which is the hourly price all customers will pay to run a Spot Instance for that given period. The Spot Price fluctuates based on supply and demand for instances, but customers will never pay more than the maximum price they have specified. If the Spot Price moves higher than a customer’s maximum price, the customer’s instance will be shut down by Amazon EC2. Other than those differences, Spot Instances perform exactly the same as On-Demand or Reserved Instances. See here for more details on Spot Instances.

Q. How do I purchase and start up a Spot Instance?

Spot Instances can be requested using the AWS Management Console or Amazon EC2 APIs. To start with the AWS Management Console:

Log in to the AWS Management Console, then click the “Amazon EC2” tab.
Click on “Spot Requests” in the navigation pane on the left.
Click on “Request Spot Instances” and proceed through the Launch Instance Wizard process, choosing an AMI, Region and instance size and type. Enter the number of Spot Instances you would like to request, your maximum price and whether the request is persistent or not. After choosing your key pair and security group(s), you are ready to submit your Spot Instance request.

For detail on how to request Spot Instances through the Amazon EC2 API, see the Amazon EC2 API Reference.

For a more detailed walk through of using Spot Instances and more information on how to get the most out of Spot Instances, please read Introduction to Spot Instances.

Q. How many Spot Instances can I request?

You can request as few as 1 or as many as 100 Spot Instances via the Amazon EC2 Management Console or API. If you need to request more than 100 Spot Instances, you can request to have your limit raised by completing the Amazon EC2 instance request form.

Q. Are Spot Instances available for all instance families and sizes and in all regions?

Yes.

Q. Which Operating Systems are available as Spot Instances?

Linux/Unix and Windows Server are available. Windows Server with SQL Server is not currently available.

Q. Are there any features or services of Amazon Web Services that are not supported for use with Spot Instances?

The following features are not yet supported for use with Spot Instances: Auto Scaling, Amazon Virtual Private Cloud, Amazon Elastic MapReduce, and Amazon DevPay.

Q. Can I use a Spot Instance with a paid AMI for third party software (such as IBM’s software packages)?

Not at this time.

Q. Will I be charged if my Spot Instance is terminated by Amazon EC2 before the hour is up?

No. If the Spot Instance is terminated by Amazon EC2, you will not be charged for a partial hour of usage. However, if you terminate the instance yourself, you will be charged for any hour in which the instance ran.

Q. How often should I expect the Spot Price to change?

Amazon EC2 will change the Spot Price periodically as new requests are received and as available Spot capacity changes (e.g. due to instance terminations). While the Spot Price may change anytime, in general the Spot Price will change once per hour and in many cases less frequently. We publish the current Spot Price and historical prices for Spot Instances through the API, which can also be viewed using the AWS Management Console; these can help you assess the levels and timing of fluctuations in the Spot Price over time.

Q. Will all Spot Instances started at the same time be charged the same price?

Yes.

Q. Will the price I’m charged for a running Spot Instance change during its instance-hour as the Spot Price changes?

No. The price per instance-hour for a Spot Instance is set at the beginning of each instance-hour for the entire hour. Any changes to the Spot Price will not be reflected until the next instance-hour begins.

Q. Where can I see my usage history for Spot Instances and see how much I was billed?

The AWS portal makes a detailed billing report available which shows Spot instance start and termination times for all instances. Customers can check the billing report against historical Spot prices via the API to verify the Spot Price they were billed is correct.

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Cluster Compute Instances

Q. What is a Cluster Compute Instance?

Cluster Compute Instances combine high compute resources with a high performance networking for High Performance Compute (HPC) applications and other demanding network-bound applications. Cluster Compute Instances provide similar functionality to other Amazon EC2 instances but have been specifically engineered to provide high performance networking.

New Amazon EC2 cluster placement group functionality allows users to group Cluster Compute Instances in clusters – allowing applications to get the low-latency network performance necessary for tightly-coupled node-to-node communication typical of many HPC applications. Cluster Compute Instances also provide significantly increased network throughput both within the Amazon EC2 environment and to the Internet. As a result, these instances also well suited for customer applications that need to perform network-intensive operations.

Learn more about use of this instance type for HPC applications.

Q. Does use of Cluster Compute Instances differ from other Amazon EC2 instance types?

Yes, Cluster Compute Instances use differs from other Amazon EC2 instance types in three ways.

First, Cluster Compute instances use Hardware Virtual Machine (HVM) based virtualization and run only Amazon Machine Images (AMIs) based on HVM virtualization. Paravirtual Machine (PVM) based AMIs used with other Amazon EC2 instance types cannot be used with Cluster Compute Instances.

Second, Cluster Compute Instances require booting from an EBS-backed AMI.

Third, in order to fully benefit from the available low latency, full bisection bandwidth between instances, Cluster Compute Instances must be launched into a cluster placement group through the Amazon EC2 API or AWS Management Console.

Q. What is a cluster placement group?

A cluster placement group is a logical entity that enables creating a cluster of instances by launching instances as part of a group. The cluster of instances then provides low latency, full bisection 10 Gigabit Ethernet bandwidth connectivity between instances in the group. Cluster placement groups are created through the Amazon EC2 API or AWS Management Console.

Q. Are all features of Amazon EC2 available for Cluster Compute Instances?

Currently, Amazon Virtual Private Cloud and Amazon DevPay are not available for Cluster Compute Instances. Also, Cluster Compute Instances do not currently support the option of using the Windows Server operating system or requesting the instances as Spot Instances. Additionally, Auto Scaling cannot currently be used to launch Cluster Compute Instances into a cluster placement group.

Q. Is there a limit on the number of Cluster Compute Instances I can use and/or the size of cluster I can create by launching Cluster Compute Instances into a cluster placement group?

By default customers are limited to a default of 8 Cluster Compute instances, but larger clusters are supported. If you need to run larger clusters, please complete the Amazon EC2 instance request form with a primary instance type of Cluster Compute Quadruple Extra Large.

Q. Are there any ways to optimize the likelihood that I receive the full number of instances I request for my cluster via a cluster placement group?

Yes. For larger clusters, you can increase the likelihood of being able to launch the total number of instances you’ll need in a cluster placement group by launching as many instances at once as possible instead of launching a few instances and then attempting to add additional instances later.

Q. If an instance in a cluster placement group is stopped then started again, will it maintain its presence in the cluster placement group?

Yes. A stopped instance will be started as part of the cluster placement group it was in when it stopped. If capacity is not available for it to start within its cluster placement group, the start will fail.

Q. Which Regions and Availability Zones will offer Cluster Compute Instances?

Cluster Compute instances are currently available in a single Availability Zone in the US – N. Virginia Region.

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Amazon EC2 Running Microsoft Windows and Other Third-Party Software

Q. Can I use my existing Windows Server license with EC2?

No, Microsoft Windows Server licensing does not currently support using your existing Windows license in Amazon EC2 or any other cloud environment. We encourage you to work with your Microsoft account representative to understand licensing options.

Q. What software licenses can I bring to the Windows environment?

Specific software license terms vary from vendor to vendor. Therefore, we recommend that you check the licensing terms of your software vendor to determine if your existing licenses are authorized for use in Amazon EC2.

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Microsoft Windows Server License Mobility Pilot

Q. What are the pilot eligibility criteria?

To participate in this pilot, Microsoft requires that you meet the following criteria:

Your company must be based (or have a legal entity) in the United States
Your company must have an existing Microsoft Enterprise Agreement (EA) that is valid for a minimum of 12 months after your entry into the pilot
You must have already purchased Software Assurance from Microsoft for your EA Windows Server licenses
You must be an Enterprise customer (Academic and Government institutions are not covered by this pilot)

Q. What Microsoft software is eligible to be used with the Windows Server Mobility pilot?

Only Standard, Enterprise, and Datacenter Editions of Windows Server licenses are eligible to be used with the Windows Server License Mobility pilot. Microsoft SQL Server, Microsoft Office SharePoint Server, and other Microsoft software is excluded from this pilot program. As always, please contact your Microsoft sales representative if you have questions regarding your specific terms associated with your licenses.

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Amazon EC2 Running IBM

Q. How am I billed for my use of Amazon EC2 running IBM?

You pay only for what you use and there is no minimum fee. Pricing is per instance-hour consumed for each instance type. Partial instance-hours consumed are billed as full hours. Data transfer for Amazon EC2 running IBM is billed and tiered separately from Amazon EC2. There is no Data Transfer charge between two Amazon Web Services within the same region (i.e. between Amazon EC2 US West and another AWS service in the US West). Data transferred between AWS services in different regions will be charged as Internet Data Transfer on both sides of the transfer.

For Amazon EC2 running IBM pricing information, please visit the pricing section on the Amazon EC2 running IBM detail page.

Q. Can I use Amazon DevPay with Amazon EC2 running IBM?

No, you cannot use DevPay to bundle products on top of Amazon EC2 running IBM at this time.

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Service Level Agreement (SLA)

Q. What does your Amazon EC2 Service Level Agreement guarantee?

The Amazon EC2 SLA guarantees 99.95% availability of the service within a Region over a trailing 365 day period.

Q. How do I know if I qualify for a SLA Service Credit?

You are eligible for a SLA credit if the Region that you are operating in has an annual availability of less than 99.95% as measured over a trailing 365-day period. For full details on all of the terms and conditions of the SLA, as well as details on how to submit a claim, please see http://aws.amazon.com/ec2-sla.

Q. What does your Amazon EC2 Service Level Agreement guarantee?

The Amazon EC2 SLA guarantees 99.95% availability of the service within a Region over a trailing 365 day period.

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Amazon EC2 running Microsoft Windows Server® 2003/2008 is a fast and dependable environment for deploying applications using the Microsoft Web Platform.

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