A while back, I wrote a post entitled How To Point Synology Backups to Amazon Glacier using IAM. Recently, Amazon has published a blog post that covers the use of Data Retrieval Policies to control the costs of retrieving data from the Glacier service.
By default, your policy will be configured as No Retrieval Limit if you were using Glacier prior to Dec 11, 2014. Anyone who starts using Glacier after that point will be set to the Free Tier Only policy as a default.
I’d advise that folks who followed my earlier article on backing up Synology to Glacier take a moment to review their retrieval policy and make adjustments as needed. I’ve gone ahead and switched to the Free Tier Only policy.
To do so, navigate to your Amazon Glacier Vaults page and click the Settings button.
Here’s a bit more information on each of the tiers, as stated by the Amazon Glacier Data Retrieval Policies document:
Free Tier Only Policy
You can set a data retrieval policy to Free Tier Only to ensure that your retrievals will always stay within your free tier allowance, so you don’t incur data retrieval charges. If a retrieval request is rejected, you will receive an error message stating that the request has been denied by the current data retrieval policy.
You set the data retrieval policy to Free Tier Only for a particular AWS region. Once the policy is set, you cannot retrieve more data in a day than your prorated daily free retrieval allowance for that region and you will not incur data retrieval fees.
You can switch to a Free Tier Only policy after you have incurred data retrieval charges within a month. The Free Tier Only policy will take effect for new retrieval requests, but will not affect past requests. You will be billed for the previously incurred charges.
Max Retrieval Rate Policy
You can set your data retrieval policy to Max Retrieval Rate to control the peak retrieval rate by specifying a data retrieval limit that has a bytes-per-hour maximum. When you set the data retrieval policy to Max Retrieval Rate, a new retrieval request will be rejected if it would cause the peak retrieval rate of the in progress jobs to exceed the bytes-per-hour limit specified by the policy. If a retrieval job request is rejected, you will receive an error message stating that the request has been denied by the current data retrieval policy.
No Retrieval Limit Policy
If your data retrieval policy is set to No Retrieval Limit, all valid data retrieval requests will be accepted and your data retrieval costs will vary based on your usage.