Do incremental off-site backups require to download previous backup(s)?

[cdhowie]

@alexweiss Note that he said:

@tomwaldnz

I’m considering an approach of doing a backup of my data to a local disk, then using the AWS command line program (aws s3 sync) to copy the restic repo up to AWS S3.

So the repository would not be directly accessed to take backups, which mitigates all of your concerns except cost.

@tomwaldnz

I understand B2 is an easier option, which is a bit cheaper than S3 IA but more expensive than S3 DA. I’m an AWS specialist and prefer to keep my data there where practical and economic, but B2 is a quality storage provider I’d consider using if I couldn’t use S3 DA.

We can calculate which will be cheaper depending on how often you need to restore. Note that to keep this calculation simple, I am going to ignore the following:

• Per-request upload and download fees.
• Per-object GDA migration fees.
• S3 housekeeping object fees.
• S3 Standard storage fees both before transitioning to GDA and for restored objects held during retrieval.

B2 costs $0.005 per GB/month for storage and $0.01 per GB for egrees.

S3 GDA costs $0.00099 per GB/month for storage and $0.09 per GB for egress, plus retrieval fees depending on how quickly you need your data:

• For access in 3-5 hours (standard), $0.02 per GB.
• For access in 5-12 hours (bulk), $0.0025 per GB.

(If you can’t wait 3 hours for a restore then GDA is disqualified on the spot.)

The final variable we have is r which is the number of times you plan to restore per year.

For each provider the yearly cost is:

12*storagerate*gb + retrievalrate*r*gb

By setting two scenarios equal and solving for r we can find the point at which both scenarios cost the same in terms of restores per year. B2 vs S3 GDA with the standard retrieval tier is thus:

12*0.005*gb + 0.01*r*gb = 12*0.00099*gb + (0.02 + 0.09)*r*gb

r = 0.4812

0.4812 restores per year works out to just over one restore every two years. So, if you are going to use GDA, this would be my plan:

• Know how much retrieval is going to cost (approx. $0.11 per GB in the repository).
• Every month make sure that you have this amount in your savings to cover a retrieval. This will “cost” more than B2 in the short term as you have to reserve more funds than you would using B2 ($0.10 more per GB).

After 2 years without a retrieval, GDA starts to save you money.

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For the sake of a complete answer, here is the calculation for the bulk retrieval tier:

12*0.005*gb + 0.01*r*gb = 12*0.00099*gb + (0.0025 + 0.09)*r*gb

r = 0.58

This is every 1.7 years instead of every 2. The standard AWS egress fees are way more of an issue than the GDA retrieval fees.