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Re: Hardware advice

From: "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>
To: Adam Witney <awitney(at)sghms(dot)ac(dot)uk>
Cc: pgsql-performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Hardware advice
Date: 2003-05-30 15:25:38
Message-ID: Pine.LNX.4.33.0305300920200.31323-100000@css120.ihs.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Fri, 30 May 2003, Adam Witney wrote:

> 250,000 rows (5-10 numeric fields per row), processing the data (I may split
> this to a second box) and then writing back ~20,000 rows of data (2-3
> numeric fields per row).

Make sure and vacuum often and crank up your fsm values to be able to 
reclaim lost disk space.

> 36Gb 10,000rpm Ultra 3 160 SCSI
> 36Gb 10,000rpm Ultra 3 160 SCSI
> 146Gb 10,000rpm U320 SCSI
> 146Gb 10,000rpm U320 SCSI
> 146Gb 10,000rpm U320 SCSI
> 
> PERC 3/DC RAID Controller (128MB Cache)

If that box has a built in U320 controller or you can bypass the Perc, 
give the Linux kernel level RAID1 and RAID5 drivers a try.  On a dual CPU 
box of that speed, they may well outrun many hardware controllers.  
Contrary to popular opinion, software RAID is not slow in Linux.  

> RAID1 for 2x 36Gb drives
> RAID5 for 3x 146Gb drives

You might wanna do something like go to all 146 gig drives, put a mirror 
set on the first 20 or so gigs for the OS, and then use the remainder 
(5x120gig or so ) to make your RAID5.  The more drives in a RAID5 the 
better, generally, up to about 8 or 12 as the optimal for most setups.

But that setup of a RAID1 and RAID5 set is fine as is.

By running software RAID you may be able to afford to upgrade the 36 gig 
drives...

> Would it be better to have a dual 2.4GHz setup rather than a single 2.8GHz
> or would it not make much difference?

Yes it would.  Linux servers running databases are much more responsive 
with dual CPUs.

> Am I overdoing any particular component at the expense of another?

Maybe the RAID controller cost versus having more big hard drives.



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