Re: Low Budget Performance, Part 2

From: "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>
To: eric soroos <eric-psql(at)soroos(dot)net>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Low Budget Performance, Part 2
Date: 2002-12-04 20:28:46
Message-ID: Pine.LNX.4.33.0212041323520.15194-100000@css120.ihs.com
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On Thu, 28 Nov 2002, eric soroos wrote:

> The rotational speed difference is 40% (10k/7.2k), and the TPS
> difference is about 60% (50/30 or 40/25)

I would suggest that areal density / xfer rate off the platters is the
REAL issue, not rotational speed. Rotational speed really only has a
small effect on the wait time for the heads to get in position, whereas
xfer rate off the platters is much more important.

My older 7200RPM 2Gig and 4Gig UW SCSI drives are no match for my more
modern 40 Gig 5400 RPM IDE drive, which has much higher areal density and
xfer rate off the platters. While it may not spin as fast, the bits /
cm2 are MUCH higher on that drive, and I can get around 15 megs a second
off of it with bonnie++. The older 4 gig UW drives can hardly break 5
Megs a second xfer rate.

Of course, on the drives you're testing, it is quite likely that the xfer
rate on the 10k rpm drives are noticeably higher than the xfer rate on
the 7200 rpm IDE drives, so that is likely the reason for the better
performance.

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