Re: Database size Vs performance degradation - Mailing list pgsql-performance

From Matthew Wakeling
Subject Re: Database size Vs performance degradation
Date
Msg-id Pine.LNX.4.64.0807301331550.4250@aragorn.flymine.org
Whole thread Raw
In response to Database size Vs performance degradation  ("Dave North" <DNorth@signiant.com>)
Responses Re: Database size Vs performance degradation
List pgsql-performance
On Wed, 30 Jul 2008, Dave North wrote:
> Running on HP DL380 w/ 4GB RAM, dual 10K HDDs in RAID 0+1

> Checking the stats, the DB size is around 7.5GB;

Doesn't fit in RAM.

> ...after the load, the DB size was around 2.7GB

Does fit in RAM.

> One observation I've made on the DB system is the disk I/O seems
> dreadfully slow...we're at around 75% I/O wait sometimes and the read
> rates seem quite slow (hdparm says around 2.2MB/sec - 20MB/sec for
> un-cached reads).

That's incredibly slow in this day and age, especially from 10krpm HDDs.
Definitely worth investigating.

However, I think vacuuming more agressively is going to be your best win
at the moment.

Matthew

--
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Librarian: "We have a table-top model over here."
Patron: "No, that's not good enough. Don't you have a life-size?"
Librarian: (pause) "Yes, but it's in use right now."

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