Amazon Web Services has always been about delivering IT on demand. Spin up a virtual server, or a few thousand, anytime you'd like. Store and access as much data as you need to your heart's content.

But even in a Web-driven world, there is need for services that don't offer instant results, but will be around for eternity (or as close as possible). So today, Amazon introduced Glacier, a data archival service that will store data for one penny per gigabyte per month. As befits its name, Glacier is designed to last for a long time, but is slow: accessing data will take three to five hours. Amazon hasn't detailed exactly what technology is storing the data, but massive tape libraries are a good bet given the lengthy retrieval windows. A ZDNet article interprets one Amazon statement to mean that the company is actually using "a multitude of high-capacity, low-cost discs," but this has not been confirmed. An Amazon statement sent to Ars says only that "Glacier is built from inexpensive commodity hardware components," and is "designed to be hardware-agnostic, so that savings can be captured as Amazon continues to drive down infrastructure costs."

We also don't know exactly how Amazon measures the reliability of its storage, but the company is promising 11 nines of annual durability (99.999999999 percent) for each item, with data stored "in multiple facilities and on multiple devices within each facility."

While Amazon says "Glacier can sustain the concurrent loss of data in two facilities," there is still risk data could be lost forever. If you store 1TB, Amazon's promised durability rate suggests you can expect to lose an average of 10 bytes per year. Amazon is betting that will be an acceptable risk for the service's low price.

Amazon CTO Werner Vogels described the new service in his blog, saying, "Building and managing archive storage that needs to remain operational for decades if not centuries is a major challenge for most organizations. From selecting the right technology, to maintaining multisite facilities, to dealing with exponential and often unpredictable growth, to ensuring long-term digital integrity, digital archiving can be a major headache. It requires substantial upfront capital investments in cold data storage systems such as tape robots and tape libraries, then there’s the expensive support contracts—and don’t forget the ongoing operational expenditures such as rent and power."

As mentioned, pricing is one cent per gigabyte per month, although that can go up to a whopping 1.1 cents if you store in Europe rather than the US, and up to 1.2 cents for storage in Japan. There is no cost to transfer data into the service over the Internet, but some customers transferring large amounts of data may end up paying for Amazon's import/export service, which involves portable storage devices shipped from the customer to Amazon.

Retrieval of storage is free if you're only grabbing 5 percent of your data per month, an Amazon announcement notes. After that, data transfer fees start at 1 cent per gigabyte, but vary widely based upon what region you're in. For example, here are the data transfer prices from Amazon's East Coast region:

For accessing 10TB, that works out to $1,200 after you've exhausted the free allotment. Transfer prices go up significantly if you're in the Asia-Pacific region, and hit their highest point in South America:

Complicating matters, the amount customers pay also takes into account hourly retrieval rates, as detailed on a Glacier FAQ.

For data that must be retrieved quickly, Amazon has long offered its Simple Storage Service (S3). Because of how the two services are priced, Amazon said that S3 will in many cases be the more cost-effective option "for data that you’ll need to retrieve in greater volume more frequently."

Glacier is really for the data you can't delete (perhaps for legal and regulatory reasons) but will hardly ever need. In that sense, Amazon is trying to displace the giant tape libraries enterprises build, or offsite archival vendors. While the service has quite a different purpose than Amazon's traditional cloud businesses, Glacier can be managed from the same console as S3 and Amazon's database services. Sometime "in the coming months" Amazon customers will be able to automatically move data between S3 and Glacier based on data life-cycle policies, much like enterprise storage systems automatically move infrequently accessed data to cheaper tiers of storage.

While Vogels' blog said Amazon will be able to meet enterprises' regulatory needs (in part with AES-256 encryption), the service also caters to small businesses without a good archiving plan, historical and research organizations, or people who work in digital media.

"Although archiving is often associated with established enterprises," because of the high upfront costs and ongoing maintenance, Vogels wrote, "many SMBs and startups have similar archival needs, but dedicated archiving solutions have been out of their reach."