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Re: Huge Data sets, simple queries

From: "Jeffrey W(dot) Baker" <jwbaker(at)acm(dot)org>
To: Luke Lonergan <LLonergan(at)greenplum(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Huge Data sets, simple queries
Date: 2006-01-29 21:04:01
Message-ID: 1138568641.10923.6.camel@noodles (view raw or flat)
Thread:
Lists: pgsql-performance
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.


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