| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | Alex Turner <armtuk(at)gmail(dot)com> |
| Cc: | Kevin Brown <kevin(at)sysexperts(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: How to improve db performance with $7K? |
| Date: | 2005-04-19 01:45:15 |
| Message-ID: | 200504190145.j3J1jFb28220@candle.pha.pa.us |
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| Lists: | pgsql-performance |
Alex Turner wrote:
> Does it really matter at which end of the cable the queueing is done
> (Assuming both ends know as much about drive geometry etc..)?
Good question. If the SCSI system was moving the head from track 1 to
10, and a request then came in for track 5, could the system make the
head stop at track 5 on its way to track 10? That is something that
only the controller could do. However, I have no idea if SCSI does
that.
The only part I am pretty sure about is that real-world experience shows
SCSI is better for a mixed I/O environment. Not sure why, exactly, but
the command queueing obviously helps, and I am not sure what else does.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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