I am confused on whether or not to consider glacier expedited retrievals for the exam.
When I see questions asking if we should advise storing files in Glacier or IA, and the aim is the lowest cost possible, I tend to think that Glacier with expedited would be the better option.
In the exam, should we go for the clearly stated (and in that case, if the answer does not contain Glacier expedited retrieval we should consider the standard Glacier SLA) or we can think about the possibility of accelerating and saving money?
Glacier now has Instant Retrieval, Flexible Retrieval and Deep Archive. The trade off is cost versus availability with cost primarily being storage, retrieval fees per GB and provisioned capacity.
I would assume that in the exam Glacier Flexible is referred to just as Glacier. Hopefully the context of the question provides the main driver to optimise e.g. cost and then lets you know how often the data is accessed and the allowed SLAs for retrieval.
Glacier Instant Retrieval is now in the mix as substitute for IA when you only need the data once or twice a year, but still require immediate access. IA is $0.01 per GB to retrieve and $0.0125 to store vs $0.03 for retrieval and $0.004 for storage for Glacier Instant Retrieval.
For Glacier Flexible Retrieval is about 3c for Expedited Retrieval, 1c for Standard and free for bulk. There is a cost if you need to reserve capacity. Storage is about 10% cheaper than Glacier Instant Retrieval.
For a cost based approach I would choose Glacier Flexible Retrieval as long as I can wear the 1-5 minutes and the $10 expedited request fee and potentially the reserved capacity costs.
The Flexible Retrieval option is appealing because you can save a lot on retrieval if you can wait for bulk uploads.
Using the calculator for 1000GB per month and 1 retrieval of 1000GB I get:
S3-IA – 22 USD (12 USD with no retrievals)
S3-Instant Retrieval – 34 USD (about 4 USD with no retrievals)
S3-Glacier (Flexible) with 1 expd request – 33 USD (only 4 USD using bulk)