Re: Huge Data sets, simple queries

On Sun, 2006-01-29 at 13:44 -0500, Luke Lonergan wrote:
> Depesz,
>
> > [mailto:pgsql-performance-owner(at)postgresql(dot)org] On Behalf Of
> > hubert depesz lubaczewski
> > Sent: Sunday, January 29, 2006 3:25 AM
> >
> > hmm .. do i understand correctly that you're suggesting that
> > using raid 10 and/or hardware raid adapter might hurt disc
> > subsystem performance? could you elaborate on the reasons,
> > please? it's not that i'm against the idea - i'm just curious
> > as this is very "against-common-sense". and i always found it
> > interesting when somebody states something that uncommon...

> Oh - and about RAID 10 - for large data work it's more often a waste of
> disk performance-wise compared to RAID 5 these days. RAID5 will almost
> double the performance on a reasonable number of drives.

I think you might want to be more specific here. I would agree with you
for data warehousing, decision support, data mining, and similar
read-mostly non-transactional loads. For transactional loads RAID-5 is,
generally speaking, a disaster due to the read-before-write problem.

While we're on the topic, I just installed another one of those Areca
ARC-1130 controllers with 1GB cache. It's ludicrously fast: 250MB/sec
burst writes, CPU-limited reads. I can't recommend them highly enough.

-jwb

PS: Could you look into fixing your mailer? Your messages sometimes
don't contain In-Reply-To headers, and therefore don't thread properly.