Re: Query Performance and IOWait

On Thu, 18 Nov 2004 12:14:00 -0500
Dave Cramer <pg@fastcrypt.com> wrote:

> Andrew,
>
> Dell's aren't well known for their disk performance, apparently most
> of the perc controllers sold with dell's are actually adaptec
> controllers. Also apparently they do not come with the battery
> required to use the battery backed up write cache ( In fact according
> to some Dell won't even sell the battery to you). Also Dell's
> monitoring software is quite a memory hog.
>
> Have you looked at top ?, and also hdparm -Tt /dev/sd?

  I haven't seen any PERC controllers that were really Adaptec ones,
  but I for one quit buying Dell RAID controllers several years ago
  because of poor Linux support and performance.

  On one machine (not a PostgreSQL server) we saw a 20% speed
  improvement by switching to software raid.

  If you have a test machine, I would suggest moving the data to a
  box without a RAID controller and see if you get better results.

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   Frank Wiles <frank@wiles.org>
   http://www.wiles.org
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