Volumes that operate with 20 GB or less of modified data since their most recent Amazon EBS snapshot can expect an annual failure rate (AFR) of between 0.1% – 0.5%, where failure refers to a complete loss of the volume. This compares with commodity hard disks that will typically fail with an AFR of around 4%, making EBS volumes 10 times more reliable than typical commodity disk drives.

Because Amazon EBS servers are replicated within a single Availability Zone, mirroring data across multiple Amazon EBS volumes in the same Availability Zone will not significantly improve volume durability.

That last sentence makes it sound like there is a 0.1% – 0.5% chance of catastrophic data loss of many distinct EBS volumes in an availability zone. If that’s the case, that’s scary – off the top of my head, I’d say your run-of-the mill “Enterprise” SAN doesn’t have a one-in-two hundred risk of catastrophic failure per year.

More links, not all of which I’ve had a chance to fully digest yet:

• Feature Guide: Elastic Block Store
• Amazon EBS (Elastic Block Store) – Bring Us Your Data
• Amazon’s Elastic Block Store explained
• Why Amazon’s Elastic Block Store Matters
• Amazon EBS – Tool and Library Support
• Running MySQL on Amazon EC2 with Elastic Block Store

• Amazon Elastic Block Store goes live! (Yeah, that link’s dead – like I said, it was later deleted.) The RightScale folks appear to have inadvertently published a draft (on 8/8, the day after I left town) of their blog post designed to coincide with the release of Amazon’s Elastic Block Store for EC2. They later deleted it, but Google Reader kindly cached the post for me. I won’t repeat anything in the post, nor would I bank on anything written there – would you gamble anything important on a retracted post about a not-yet-released product? I will add one comment: Will EBS attract attention of the lawsuit kind from NetApp? (I mean that comment only partially in jest – and you’d probably have to have seen the original post to know what I’m talking about.)