Release: Amazon EC2 on 2011-05-26

Release Notes>Amazon EC2>Release: Amazon EC2 on 2011 05 26
Support for Amazon Spot Instances Availability Zone Local Pricing Changes and a new API version: 2011-05-15.


Submitted By: Francis@AWS
Release Date: May 26, 2011 7:00 AM GMT
Latest Version: 2011-05-15
Latest WSDL:
Created On: May 27, 2011 6:24 AM GMT
Last Updated: May 27, 2011 6:24 AM GMT

New Features

Availability Zone Pricing for Spot Instances We introduced a Spot Instance price per Availability Zone rather than a Spot Instance price for an entire Region (covering all Availability Zones within the Region). This improved pricing granularity will enable you to determine the price required to launch a Spot Instance into a specific Availability Zone.

As a part of this launch, we updated two APIs:

  • DescribeSpotPriceHistory returns the price history sorted from most recent to oldest for each Availability Zone (rather than Region). To reduce the amount of data returned, we have also added parameters to allow you to paginate your results. For customers using WSDL 2011-02-28 or earlier, you will now receive the Spot price history for the lowest priced Availability Zone over time. These results will be sorted from oldest to newest.
  • DescribeSpotInstanceRequests includes an Availability Zone parameter that allows you to determine the Availability Zone in which your bid was launched.

If you are an existing user, we suggest that you review your scripts to determine if these changes may affect you. For example:

  • If you have a script that creates requests to target a particular Availability Zone, you might want to update your scripted bidding strategy to take advantage of the additional data now available.
  • If you have automated scripts that try to determine why your instance was interrupted, you might want to update your scripts. Specifically, you could use the DescribeSpotRequests API to determine which Availability Zone your instance was in, and then the new DescribeSpotPriceHistory API to determine how the price might have changed. If you are using an earlier version of the WSDL, we will return the lowest price in the Availability Zone, so you will no longer be able to determine why you were interrupted.
  • If your script assumes that the order of the DescribeSpotPriceHistory results are sorted oldest to newest, you will want to make sure to update your script to assume that the order of the DescribeSpotPriceHistory results are sorted from newest to oldest when you upgrade to the latest WSDL.

Known Issues

Current Limitations for VM Import Following are current limitations of VM Import:
  • Windows Server 2003 is currently not supported

  • The following types of images currently cannot be imported into Amazon EC2:
    • VMware Workstation VMDK images
    • Encrypted, compressed, or read-only images
    • Started or suspended images
    • Linked clones
    • Images with multiple virtual disks

  • When you import a disk image to an Amazon EC2 instance, the instance appears in the AWS Management Console before the conversion process finishes. To determine when the process is complete and the instance is available to use, use the ec2-describe-conversion-tasks command.
Current Limitations for Cluster Instances Following are current limitations of cluster compute and cluster GPU instances:
  • Only the US-East (Northern Virginia) Region supports cluster instances
  • Microsoft Windows Server is not supported
  • Spot Instance requests are not supported
  • Amazon Virtual Private Cloud is not supported
  • Amazon DevPay is not supported
Current Limitations for Cluster Placement Groups Following are current limitations of cluster placement groups:
  • Reserved Instances are not currently available within a cluster placement group
Current Limitations for Tags and Filters You currently cannot tag the following resources:
  • Elastic IP addresses
  • Key pairs
  • Placement groups
You can currently filter your resources in the AWS Management Console by tag, but not by the other filters that are available to use with Describe* actions through the command line tools or API.
Current Limitations for Micro Instances Following are current limitations of micro instances:
  • Amazon Virtual Private Cloud is not supported
  • Amazon Elastic MapReduce is not supported
  • Amazon DevPay is not supported
Instance Clock Drift Some instances (Windows instances in particular) can experience a system clock drift. The issue appears to be more severe in t1.micro Windows instances that run CPU-intensive workloads. If your application is sensitive to time drift, consider using other instance types until a resolution is available.
Setting the TCP_MAXSEG Socket Option The 2.6.18-164.15.1 kernel used in the CentOS 5.4 reference AMI (ami-7ea24a17) contains a known issue: Setting the TCP_MAXSEG socket option on TCP sockets to certain values (e.g., 1500) causes the kernel to generate TCP Segmentation Offload (TSO) packets with invalid sizes that the NIC driver then drops. The impact is significantly lower network throughput. As a workaround, don't set this socket option and let the kernel use the default settings to handle segmentation and Path Maximum Transmission Unit (PMTU) discovery.
Query Version of ModifyInstanceAttribute The ModifyInstanceAttribute action currently does not allow you to modify the block device mapping for the instance.
Paid AMIs Backed by Amazon EBS Amazon EBS-backed AMIs are not currently supported by Amazon DevPay.
Windows AMI Launch Times Windows AMIs take longer to launch than Linux/UNIX instances due to larger AMI sizes and multiple reboots.
Windows AMI Sizes Installing software on Amazon S3-backed Windows AMIs can cause them to become large and easily reach the 10 GB limit. Before bundling, check the size of the C:\ volume.
Limitation on Drive Mapping There are limitations on devices available for storage attachment. For more information, go to How to Attach the Volume to an Instance in the Amazon Elastic Compute Cloud User Guide.
Instance Limit New AWS accounts are limited to a maximum of 20 concurrent instances, but many of our customers use hundreds or thousands of instances. If you need a higher limit, go to
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