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Re: advice on raid controller

From: "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>
To: Matt Clark <matt(at)ymogen(dot)net>
Cc: <rj(at)last(dot)fm>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: advice on raid controller
Date: 2003-09-29 13:48:35
Message-ID: Pine.LNX.4.33.0309290746540.14302-100000@css120.ihs.com (view raw or flat)
Thread:
Lists: pgsql-performance
I've used the megaraid / LSI cards in the past and they were pretty good 
in terms of reliability, but the last one I used was the 328 model, from 4 
years ago or so.  that one had a battery backup option for the cache, and 
could go to 128 Meg.  We tested it with 4/16 and 128 meg ram, and it was 
about the same with each, but we didn't do heavy parallel testing either.

Here's the page on the megaraid cards at lsilogic.com:

http://www.lsilogic.com/products/stor_prod/raid/ultra320products.html

On Sun, 28 Sep 2003, Matt Clark wrote:

> As others have mentioned, you really ought to get battery-backed cache if
> you're doing any volume of writes.  The ability to do safe write-back
> caching makes an *insane* difference to write performance.
> 
> The site you link to also has that for only 15% more money:
> http://uk.azzurri.com/product/product.cgi?productId=80
> 
> No experience with the card(s) I'm afraid.
> 
> In general though, U320 will only be faster than U160 for large sequential
> reads, or when you have silly numbers of disks on a channel (i.e. more than
> 4/channel).  If you have silly numbers of disks, then RAID5 will probably be
> better, if you have 4 disks total then RAID1+0 will probably be better.  In
> between it depends on all sorts of other factors.  Bear in mind though that
> if you *do* have silly numbers of disks then more channels and more cache
> will count for more than anything else, so spend the money on that rather
> than latest-and-greatest performance for a single channel.
> 
> HTH
> 
> Matt
> 
> > -----Original Message-----
> > From: pgsql-performance-owner(at)postgresql(dot)org
> > [mailto:pgsql-performance-owner(at)postgresql(dot)org]On Behalf Of Richard
> > Jones
> > Sent: 27 September 2003 18:25
> > To: pgsql-performance(at)postgresql(dot)org
> > Subject: [PERFORM] advice on raid controller
> >
> >
> > Hi, i'm on the verge of buying a "MegaRAID SCSI 320-2" raid controller.
> > I need it to build a db server using 4x ultra320 scsi disks
> > i'm thinking raid 1+0 but will try with raid5 too and compare
> >
> > Does anyone have any experience with this model, good or bad i'd like to
> > know.. thanks :)
> >
> > as seen:
> > http://uk.azzurri.com/product/product.cgi?productId=188
> >
> > Regards,
> > Richard.
> >
> > PS: whoever mentioned starting a site with raid controller
> > reviews, excellent
> > idea - its hard to find decent info on which card to buy.
> >
> >
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