Amazon S3 is an on-cloud storage service used in a variety of scenarios. On of these common scenarios is the one where you upload your server backups to S3 using any of the multiple convenient libraries and tools.
In the other hand, Amazon offers another service more oriented to data archiving and backup named Amazon Glacier. If you store a lot of data (and I am not talking about a couple of GB) then you can save money using Glacier instead of S3. Although the S3 service is sold as "infinitely scalable and highly durable" the bills work the same way and if you store TB than you might consider moving to Glacier.
Now S3 offers an option to automatically move (or delete) data from the S3 buckets to Glacier. It is called "Lifecycle" an you'll find it when logging to the AWS Console and showing the Properties tab.
From there you can create a rule that when an object is XX days old it will be moved from S3 to Glacier automatically (charges apply), or you can delete it as well.
Now it's time to make numbers, the difference in pricing between S3 and Glacier is huge.
- Save data in S3 (US Standard): $0.125 per GB up to 1TB. More expensive beyond that space used.
- Save data in Glacier(US East Virginia): $0.01 per GB / month