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Re: advice on raid controller

From: "Matt Clark" <matt(at)ymogen(dot)net>
To: <rj(at)last(dot)fm>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: advice on raid controller
Date: 2003-09-28 12:07:57
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
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:

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.



> -----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:
> 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.
> ---------------------------(end of broadcast)---------------------------
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