Amazon SimpleDB is now in public beta. This database-as-a-service has been in private beta for some time, but what’s really noteworthy is that with the public beta, Amazon has dropped the price drastically, and the first 25 machine hours, 1 GB of storage, and 1 GB of transfer are free, meaning that it’s essentially free to experiment with.

On another Amazon-related note, my colleagues who cover storage have recently put out a research note titled, “A Look at Amazon’s S3 Cloud-Computing Storage Service“. If you’re a Gartner client contemplating use of S3, I’d suggest checking it out.

I want to stress something that’s probably not obvious from that note: You can’t mount S3 storage like a normal filesystem. You access it via its APIs, and that’s all. If you use EC2 and you need cloud storage that looks like a regular filesystem, you’ll want to use Amazon’s Elastic Block Store. If you’re using S3, whether within EC2 or from your own infrastructure, you’re either going to make API calls directly (which will make your apps dependent upon S3), or you’re going to have to have to go through a filesystem driver like Fuse (commercially, Subcloud).

Cloud storage, at this stage, is typically reliant upon proprietary APIs. Some providers are starting to offer filesystems, such as Nirvanix‘s CloudNAS (now in beta), but we’re at the very earliest stages of that. I suspect that the implementation hurdles created by API-only access, and not the contractual issues, will be what stop enterprises from adopting it in the near term.

On a final storage-related note, Rackspace (Mosso) Cloud Files remains in a definitively beta stage. I was playing with the shell I was writing (adding an FTP-like get and put with progress bars and such), and trying to figure out why my API calls were failing. It turned out that the service was in read-only mode for a while yesterday, and even read calls (via the API) were failing for a bit (returning 500 Internal Server Error codes). On the plus side, my real-time chat — Rackspace’s support via an instant-messaging-like interface — support request, which I made to report the read outage, was answered immediately, politely, and knowledgeably, one clear way that the Rackspace offering wins over S3. (Amazon charges for support.)