Efren Castro ([log in to unmask]) wrote:
: We are updating our 932 to a 928. We currently have 2 -  2Gig , 1 - 4Gig
: and 4 small HP-IB drives.  We want to upgrade to a 928 with 2 9Gig
: drives.  I've heard that the 9Gig drives are very slow making the 928
: just as slow as the 932.  Is this correct ?
: For those who are on a 928 how do you like it ? Is it worth upgrading ?

9Gig drives aren't inherently slower than the drives that you currently
have.  However, your proposed change to your disc farm could have significant
impacts on system performance.

In general, MPE/iX works best if the number of I/Os per LDEV is in the
15-20 I/Os per second range.  Generally, when the disc I/O activity is in this
range, the system's performance is not I/O bound.  So lets say that on your
system, you are doing 80 I/Os per second across your 7 disc drives.  Chances
are that your system is not limited by the disc I/O activity.  However, if you
reduce the number of disc drives from 7 to 2, then you will be trying to do
40 I/Os per second per drive.  I guarantee that you will see a dramatic
reduction in your system's performance.  On the other hand, if your system is
only doing 30 I/Os per second across all 7 drives, then you are probably OK
in reducing the number of discs down to 2.

So, before making the change you suggest, be sure you understand the
performance of your current disc subsystem.

Mike P.
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Mike Paivinen
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Hewlett-Packard
CSY - Mailstop 47UA
19447 Pruneridge Avenue
Cupertino, CA   95014