On Tue, 16 Jun 2009, Just Someone wrote:
> In case the volume got corrupted (a very rare situation, as the EBS
> volumes are very durable), there are snapshots I can recover from and
> the WAL files I stream to another storage system (Amazon's S3).
I wouldn't go so far as to say "very durable", because the failure rate
they aim for isn't really very high relative to what people expect when
you use that term in a database context. The most definitive commentary
I've found on this is at
http://solutions.amazonwebservices.com/connect/thread.jspa;jsessionid=96A862FA1DC393FCDD94DAF0B43CF4E7?messageID=111953
where they say "we aim to provide an annual failure rate (AFR) of 0.1% -
0.5% for volumes"; frankly, that's garbage to most database people. But,
as you say, when combined with an alternative backup strategy when that
happens, the easy provisioning and such can give a reasonable system
design for some goals. You just have to recognize that the volumes are
statistically pretty fragile compared to a traditional RAID configuration
on dedicated hardware and plan accordingly.
--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD
