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From: McGuire_Ed@GRINNELL.MAILNET.UUCP
Newsgroups: mod.computers.vax
Subject: (none)
Message-ID: <8703150359.AA26571@ucbvax.Berkeley.EDU>
Date: Fri, 13-Mar-87 23:52:00 EST
Article-I.D.: ucbvax.8703150359.AA26571
Posted: Fri Mar 13 23:52:00 1987
Date-Received: Sun, 15-Mar-87 13:36:39 EST
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> While studying the Guide to VAXclusters about dual-pathed disks (connected to
> 2 HSC's) I began to wonder how to achieve load-balancing between the 2
> HSC's if you use allocation-classes.
>
> I would like one half of our dual-pathed disks have their primary path on
> HSC1 and failover to HSC2 and the second half of the dual-pathed disks with
> their primary path on HSC2 and failover to HSC1.
>
> Assuming both RA81 port select buttons should be pressed to enable automatic
> failover, the path that is chosen is probably arbitrary (the device-name in
> the mount-command includes an allocation class which points to both HSC's).
> Is it possible to mount a dual-pathed disk in such a way you have influence
> on the choice of the primary path ?
>
> We don't like pushing buttons every boot.
>
> Any experiences/ideas ?
>
> -----------
> Kees.       s211keno@htikht5.bitnet

Anyone I've talked to says that an HSC has such a high bandwidth that it isn't
practical to try to balance the load yourself.  Before you get very involved
in this project, look at monitor statistics and compare disk I/O response time
on disks that were mounted by different HSCs.  Details on computing disk I/O
response time can be found in _Guide to VAX/VMS Performance Management_,
section 3.7.

Ed McGuire
Grinnell College
MCGUIRE@GRIN2.BITNET