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EBS EC2 Snapshots as Incremental Backups

I understand that AWS snapshots can create incremental backups of EBS volumes. Does AWS automatically handle the incremental part (i.e., only save what has changed) while snapshots are generated from the same volume?

It’s not clear to me because they don’t list the actual size of the pictures or allow you to view them on S3 (as far as I know). There are no associated snapshots with snapshots except the volume from which they were created. Could any pictures taken (including the first) just be considered an increase in the original AMI? I would be interested to know if this is actually implemented, or if the first snapshot is a completely independent image stored in my personal S3 account.

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amazon-web-services amazon-ebs
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Each EBS snapshot only gradually adds blocks that have changed since the last snapshot.

Each EBS snapshot has all the blocks that were ever used on an EBS volume. You can delete any snapshot without reducing the completeness of any other snapshot.

This is magic.

Well, actually this is a bit of a technological focus, when each shot has pointers to blocks that it likes, and several shots can share the same blocks. As long as there is at least one snapshot that points to a specific data set on the block, the block is stored on S3.

This prevents Amazon from telling you how much space a single shot takes, because their sizes are not mutually exclusive.

Here's an old RightScale article that has some pretty pictures explaining how snapshots work behind the scenes:

http://blog.rightscale.com/2008/08/20/amazon-ebs-explained/

Note that snapshots only save blocks on the EBS volume that were used, and snapshots are compressed, which further reduces the cost of storing data.

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