| From: | Gaetano Mendola <mendola(at)bigfoot(dot)com> |
|---|---|
| To: | pgsql-general(at)postgresql(dot)org |
| Cc: | Stephen <jleelim(at)xxxxxx(dot)com> |
| Subject: | Re: VACUUM degrades performance significantly. Database |
| Date: | 2003-10-19 20:02:11 |
| Message-ID: | 3F92EDC3.5010602@bigfoot.com |
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| Lists: | pgsql-general |
Stephen wrote:
> Good news,
>
> I partially fixed the problem on Linux 2.4. It appears the responsiveness
> can be improved significantly by tuning the disk IO elevator in Linux using
> "elvtune" in util-linux. The elevator in Linux is used to re-order
> read/write requests to reduce disk seeks by ordering requests according to
> disk sectors. Unfortunately, the elevator in kernel 2.4 is not very smart
> (or flexible I should say depending on your needs) and can starve a
> read/write request for a long time if not properly tuned.
> elvtune -r 2048 -w 8192 /dev/hdc (default Redhat 9):
> ====================================================
Are you sure ? In my RH9.0 installation I obtain:
# elvtune /dev/sda7
/dev/sda7 elevator ID 5
read_latency: 64
write_latency: 8192
max_bomb_segments: 6
may be your problem is due the fact that someone change these values
on your machine!
Regards
Gaetano Mendola
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