I know how to create a snapshot of a single EBS volume. What is the best way to create snapshots of all the EBS volumes that are part of a RAID array?

When you take a snapshot of an attached Amazon EBS volume that is in use, the snapshot excludes data cached by applications or the operating system. For a single EBS volume, this is often not a problem. However, when cached data is excluded from snapshots of multiple EBS volumes in a RAID array, restoring the volumes from the snapshots can degrade the integrity of the array.

When creating snapshots of EBS volumes that are configured in a RAID array, it is critical that there is no data I/O to or from the volumes when the snapshots are created. RAID arrays introduce data interdependencies and a level of complexity not present in a single EBS volume configuration.

To create an "application-consistent" snapshot of your RAID array, stop applications from writing to the RAID array, and flush all caches to disk. Then ensure that the associated EC2 instance is no longer writing to the RAID array by taking steps such as freezing the file system, unmounting the RAID array, or shutting down the associated EC2 instance. After completing the steps to halt all I/O, take a snapshot of each EBS volume.

If you restore the EBS volumes from snapshots, be sure to stop all I/O activity, and then reverse the process you used to create the snapshots. For example, start the EC2 instance if it was shut down, mount the RAID array if it was unmounted, and start the application that was stopped.

Amazon Elastic Block Store, RAID, snapshot, performance, troubleshoot


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