Re: VACUUM degrades performance significantly. Database

Nope, I installed the RedHat 9 myself and no one else has access to this
machine. It's either that Redhat uses a different elevator setting for SCSI
drives than IDEs or the latest Redhat updates I applied brought it to my
current numbers. Besides, I believe your values may indicate an outdated
system because IIRC the max_bomb_segments has been disabled and should
always be zero because of some inefficiencies in the elevator algorithm.

Regards, Stephen

"Gaetano Mendola" <mendola(at)bigfoot(dot)com> wrote in message
news:3F92EDC3(dot)5010602(at)bigfoot(dot)com(dot)(dot)(dot)
> 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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