|Type of site||Online backup service|
|Launched||August 21, 2012|
Glacier is part of the Amazon Web Services suite of cloud computing services, and is designed for long-term storage of data that is infrequently accessed and for which retrieval latency times of 3 to 5 hours are acceptable. Storage costs are a consistent $0.01 per gigabyte per month, which is substantially cheaper than their own Simple Storage Service (S3) service.
ZDNet says, that according to private e-mail, Glacier runs on "inexpensive commodity hardware components," which are suggested to be high numbers of high-capacity low-cost hard disks. It is possible that custom low-RPM hard drives are used in custom racks with proprietary logic.
There is some confusion amongst users that the underlying hardware used for Glacier storage is tape-based, owing to the fact that Amazon has positioned Glacier as a direct competitor to tape backup services (both on-premises and cloud-based). This confusion is exacerbated by the fact that Glacier has similar archive retrieval delays to that of tape-based systems (3-5 hours before archives are available). However, all publicly available information (including communications with Amazon itself) appears to support the claim that Glacier is backed by inexpensive commodity hard drives and not tape.
While an unlimited amount of data can be uploaded for storage, the pricing structure for downloading data (retrieval) is far more complex. Getting data out of Glacier is a two-step process. The first step is to retrieve the data from Glacier staging area, subject to Glacier retrieval pricing. The next step is to actually download (transfer) the data. While Glacier advertises a free 5%/month allowance, this 5% is spread out evenly across the number of hours in a month for a 0.006944% free retrieval per hour (assuming a 30 day month). Exceeding the hourly allowance (aka peak hourly rate) at any time results in a peak retrieval overage charge that gets multiplied by the number of hours in a month.
In the more practical terms, Glacier users need to break up any sizeable retrievals across the longest period of time practical to eliminate or minimize overage charges. Developers who are planning to implement Glacier support in their applications also need to implement a mechanism for spreading out data retrieval over a long period of time, and to be extremely careful with their testing: a simple mistake or misunderstanding can easily result in a massive bill. In one example, a user stored 15GB of data in Glacier, retrieved 693MB for testing, and ended up being charged for 126GB due to retrieval rate calculation.
Uploading data to Glacier is free, but downloading data from Glacier may be charged. Data transfer to the EC2 cloud in the same region is free, while data transfer between AWS regions is charged with $0.02 per GB ($0.09 per GB if data is downloaded from Tokyo region). Data transfer from Glacier to the Internet is free up to 1 GB per month, after which a sliding scale fee starts at $0.12 per GB. Data stored in Glacier but which is deleted after being stored for a period of less than 3 months incurs a charge of $0.03 per GB, a move designed to discourage the service's use in cases where Amazon's other storage offerings (e.g. S3) are more appropriate for real-time access.
Glacier is up to 90% cheaper than AWS S3, which in the past was the only way of archiving on the AWS cloud.
- Mlot, Stephanie (August 21, 2012). "Amazon Launches Glacier Cloud Storage Service". PCMag.com (Ziff Davis, Inc.). Retrieved 2012-08-21.
- Clark, Jack (August 21, 2012). "Amazon launches Glacier cloud storage, hopes enterprise will go cold on tape use". ZDNet (CBS Interactive). Retrieved 2012-08-21.