Glacier: When slow storage retrieval wins the day

Amazon has started offering a cloud-based service specifically for long-term archiving that government users might find attractive. Rather than touting the quick response and large bandwidth that most cloud storage services boast, Amazon will in fact tell you that its Glacier service is just the opposite.

It differs a great deal from the company's Simple Storage Service (S3) in other ways as well. Files stored using S3 are available pretty close to instantly --  a couple hundred milliseconds per request at its slowest. Retrieval requests for Glacier are put into a queue and you will have access to your files in a matter of hours. Also, it costs nothing to retrieve files when using S3, while any data retrieved from Glacier will cost you for every gigabyte retrieved over 5 percent of your average monthly storage. And this is prorated per day, so every day of a 30-day month you would only be able to retrieve about 0.17 percent of your stored data for free.

But overall, where Glacier outshines its cousin S3 is on price. For this service Amazon is asking for only one cent per gigabyte per month. That is about a tenth of the cost of S3 at its lower pricing levels. That is at the optimum level of cost per gigabyte over time that large tape library servers offer, without any huge initial capital expenditure. For those agencies or offices, particularly smaller ones, that have no long-term archival solution in place, Glacier might be just what they need. It could be a great solution for storing any files that an agency needs to keep for compliance purposes.

However, it's important to keep in mind that Glacier is definitely designed for long-term data storage, and the pricing reflects that. If you end up going over your free daily limit on retrievals, or keep requesting to delete files before they’ve been in storage for 90 days, then the fees you accumulate could easily add up to more than what a standard cloud service like S3 would cost. But if you just want a place to store files that  that you rarely need to access or modify, then a service like Glacier could end up saving money.

This article on the Data Center Knowledge website has some more observations about the service, the equipment it uses, and some cost analysis. It is worth a look if you are considering using this service.

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