Re: Possible Redundancy/Performance Solution

[Greg Smith <gsmith(at)gregsmith(dot)com>]

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(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD