While Glacier allows companies to transfer their data-archiving duties to the cloud—a potentially money-saving boon for many a budget-squeezed organization—the service comes with some caveats. Its cost structure and slow speed of data retrieval make it best suited for data that needs to be accessed infrequently, such as years-old legal records and research data.
If that sounds quite a bit like Amazon Simple Storage Service, otherwise known as Amazon S3, you’d be correct. Both Amazon S3 and Glacier have been designed to store and retrieve data from anywhere with a Web connection. However, Amazon S3—“designed to make Web-scale computing easier for developers,” according to the company—is meant for rapid data retrieval; contrast that with a Glacier data-retrieval request (referred to as a “job”), where it can take between 3 and 5 hours before it’s ready for downloading."