Rackspace uses a container storage method where applications talk via an API. In turn, the API supports Ruby, PHP, Python, Java, C#/.Net, which run over an HTTPS REST transport. It's all coded, but it's not complex to do.
Rackspace charges customers for storage (15 cents per gigabyte per month), bandwidth "in" (8 cents per gigabyte per month) and "out" (22 cents per gigabyte per month), and requests (free for files over 250KB, 1 cent for files under 250KB.)
Rackspace CloudFiles has support included in its cost, and we found the support to be responsive. We did, however, have an ongoing issue with Rackspace where upload speed vastly exceeded download. In fact, the ratio was about 4 to 1.
Like the other products in this comparison, we slammed Rackspace hard, via Rackspace's Ruby API calls. We uploaded and downloaded 20 small, 20 midsize, 10 large and three extra large files.
We discovered that there are some limitations to Rackspace CloudFiles. You can build large file objects, but they can't be larger than 5GB. There are no subdirectories, per se, but it's easy to build subdirectory translation into filenames, and the third party client software we used can simulate folders pretty simply.
There is no file locking, so opening a stored object for writing needs to either be highly arbitrated, or exclusive to a single session — otherwise multiple object writers can destroy the object's data integrity.
CloudFiles, when lacking a third-party emulator, is a file object repository rather than a file system familiar to end users.
Objects aren't inherently encrypted. The transport, SSL, is encrypted, but if you want to mask the object's contents through encryption, you need to manage this yourself with CloudFiles. This isn't a showstopper, rather an alarm for those that must adhere to encrypted data rules.
Rackspace uses a Web control panel at www.rackspacecloud.com to permit users to obtain a key for access to storage areas. The only authentication possible is the use of that API access key, plus a user name. There are no other permissions, access controls, or ACLs for full read/write permission to stored objects.
For this reason, native access to Rackspace's CloudFiles storage objects are likely to revolve around Web apps, backups, temporary storage and file distribution — or those apps managed in conjunction with applications that we reviewed in prior tests of cloud automation tools and cloud management systems.
It should also be noted that Rackspace, like Amazon and other cloud hosts tested, are evolving an impressive list of third-party added-value hosting partners that augment features — often for specific vertical market application storage.