Regardless of Amazon...
first of all there are two types of snapshots. One is Full and second is Incremental. In your example you mention 10GB and 1GB so you can guess which one is which. Without a Full snapshot it is not possible to recover the data entirely if at all. Incremental snapshot is a way of saving space and time so as not to backup the whole image over and over again. So while you can retain zero incremental snapshots you must have ATLEAST one Full snapshot.
The restore is done in the following way.
1. get the Latest FULL snap
2. Is there any more incremental snap since the last full backup?
2.1 Apply the incremental changes in order from the last full backup to the latest | END
You can therefore plan how much you need. Maybe a full backup once a week and incremental everyday? or whatever suits your case. However amazon differs here a bit...
As for the cost it seems Amazon is assuming (for sake of simplicity on their part) that the
- Entire EBS is snapshotted(not a real word, i just made it up)
including the free space.
- Also compression is not accounted for and if they are compressing its
still not considered here.
- a Full snapshot or incremental will all go to S3 uncompressed so you 'll
be paying for S3 storage and transfers
- A full snapshot is more like an AMI already. So you're better of using an
AMI as the AMI does not seem to
include the unused space for the image
size and therefore the S3 storage
equirement is smaller.
- as mentioned by others Amazon protects users from deleting the wrong snaps by making >sure deletion of snaps does not affect recovery. I think they internalize the process where > they will apply the incremental snap to the full one and display it as delete. effect they > still store the whole EBS volume once
Now I am not a pro at AWS but this is to the best of my understanding. I could be wrong