29th
EBS Durability
See: http://aws.amazon.com/ebs/
It’s pretty clearly disclosed that EBS volumes aren’t terribly durable. So in fairness, it is what it is and is disclosed as it is.
An annual failure rate for a volume of 0.1% – 0.5% is mentioned. That means you should be prepared to lose a volume: it could happen. Backups / snapshots would suffice if you don’t mind losing your data since the last backup (unlikely). If you do mind, use database replication to a separate availability zone or region.
An AFR of 0.1% – 0.5% is quite a bit lower than that of a single drive, but is pretty high compared to a high end SAN product’s probability of losing data. Of course, those can be extremely expensive so this is a bit apples and oranges.
For me, for most problems I’d be quite comfortable using EBS if I’m continuously replicating my database(s) to a second region.
