There isn't much of a problem per say...
If you have a mod-3, you can do xxx amount of I/Os per second before
hitting a performance problem.
If you have 3 mod-3, you can do 3*xxx amount of I/Os per second.
However a mod-9 can only do about xxx amount of I/Os per second.
So, if you are pounding the drives, you need more addresses per GB. If
they are lightly used, or the application(s) basically single thread the
I/Os, then larger volumes have no problems.
However, you mentioned Oracle. The question that I keep posing
(because I don't know the true answer), is...
Will Oracle schedule concurrent I/Os based on dasd exposures? (dasda1,
dasdb1, dasdc3, having the ability to do an I/O on each one,
concurrently), or will it throttle concurrent I/Os based on something
else?
Perhaps LVM isn't good for Oracle, if it sees everything as one disk.
BTW, zVM 5.1 does support PAV for guests, including z/Linux. But PAV
is a chargable feature on dasd subsystems.
Tom Duerbusch
THD Consulting
>>> [EMAIL PROTECTED] 10/18/05 9:31 AM >>>
We're running VM 5.1 with SLES9 and Oracle, currently using SHARK dasd
emulating 3390-3. Our dasd folks want to know if we have any problems
with the SHARK dasd emulating 3390-9. I believe everything supports that
ok, but I'm wondering what perfomance considerations there might be both
pro and con to using 3390-9 emulation? I would appreciate any
information/experiences that anybody might have.
Thank You.
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