Re: Possible Redundancy/Performance Solution

Greg Smith wrote:
> On Tue, 6 May 2008, Dennis Muhlestein wrote:
>
>
> RAID0 on two disks makes a disk failure that will wipe out the database
> twice as likely.  If you goal is better reliability, you want some sort
> of RAID1, which you can do with two disks.  That should increase read
> throughput a bit (not quite double though) while keeping write
> throughput about the same.

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?

>
> If you added four disks, then you could do a RAID1+0 combination which
> should substantially outperform your existing setup in every respect
> while also being more resiliant to drive failure.
>
>> Our applications are mostly read intensive.  I don't think that having
>> two databases on one machine, where previously we had just one, would
>> add too much of an impact, especially if we use the load balance
>> feature of pgpool as well as the redundancy feature.
>
> A lot depends on how much RAM you've got and whether it's enough to keep
> the cache hit rate fairly high here.  A reasonable thing to consider
> here is doing a round of standard performance tuning on the servers to
> make sure they're operating efficient before increasing their load.
>
>> Can anyone comment on any gotchas or issues we might encounter?
>
> Getting writes to replicate to multiple instances of the database
> usefully is where all the really nasty gotchas are in this area.
> Starting with that part and working your way back toward the front-end
> pooling from there should crash you into the hard parts early in the
> process.


Thanks for the tips!
Dennis