On Tue, 6 May 2008, Dennis Muhlestein wrote:
> I was planning on pgpool being the cushion between the raid0 failure
> probability and my need for redundancy. This way, I get protection against
> not only disks, but cpu, memory, network cards,motherboards etc. Is this
> not a reasonable approach?
Since disks are by far the most likely thing to fail, I think it would be
bad planning to switch to a design that doubles the chance of a disk
failure taking out the server just because you're adding some server-level
redundancy. Anybody who's been in this business for a while will tell you
that seemingly improbable double failures happen, and if were you'd I want
a plan that survived a) a single disk failure on the primary and b) a
single disk failure on the secondary at the same time.
Let me strengthen that--I don't feel comfortable unless I'm able to
survive a single disk failure on the primary and complete loss of the
secondary (say by power supply failure), because a double failure that
starts that way is a lot more likely than you might think. Especially
with how awful hard drives are nowadays.
--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD