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I have 3 SSD EBS volumes mounted to my database server. The main data volume is 10TB, the journal volume is 1TB, and a 3rd volume is 100GB.

When I take a snapshot of the 3 volumes, the 1TB journal volume consistently takes much, much longer to snapshot than the 10TB data volume, even though there's only about 100GB of space used on it. (It's been over 8 hours, and it's only 55% done. The 10TB snapshot finished after about 2 hours).

Is there anything I can do to speed up the process?

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The amount of time it takes EC2 to build a snapshot is directly proportional to the number of modified blocks that volume has seen since the last snapshot. In the case of your journal, that sees a lot of write/delete operations, so it's not surprising that it would take a long time to snap.

Keep in mind that these are truly block devices. They know nothing about your filesystem. It may be true that the journal volume only has 100GB used at the moment, but since the last snapshot, every single one of its blocks may have been modified. Some of those files that occupied those blocks have been deleted, so they don't appear "used" to your filesystem, but the block device itself knows nothing about that, so it has to snap all of that data. (As an aside, this is the same reason why AWS can't report on how much data is being stored in EBS volumes without a server-side agent that can query the storage at a filesystem level.)

To mitigate, you can try and take more frequent snapshots.

One question, though...why do you care how long it takes? Once the API call returns from your snap create request, you are free to continue using the volume, and any subsequent modifications to the block device will not be included in the snapshot.

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    We will be using the snapshot process to do a migration, and I need to verify the time required. – chris May 20 '15 at 15:45

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