Re: VIOS and Perf Monitoring

According to multiple IBM and NON-IBM sources the answer is along these
lines...
The OS has no idea if these disks are real or virtual. The OS will only
queue so many I/Os per disk arm available ( I think I got that right ). So
if the OS only sees one 280GB disk it will not handle I/O as well vs having
eight 35GB disk arms. Now the actual number of real disks arms will affect
how well this concept works.

On Wed, Aug 24, 2011 at 1:17 PM, <rob@xxxxxxxxx> wrote:

I am still not getting why the OS needs to see multiple arms if they are
all virtual. Instead of one bigger virtual. It's still physically spread
across the multiple arms defined either in VIOS or your hosting partition.
Is it some weird thing like "let's calculate your journal receiver size
based on the number of arms you have"?


Rob Berendt
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From: Kirk Goins <kirkgoins@xxxxxxxxx>
To: Midrange-L <midrange-l@xxxxxxxxxxxx>
Date: 08/24/2011 04:12 PM
Subject: VIOS and Perf Monitoring
Sent by: midrange-l-bounces@xxxxxxxxxxxx



I am getting ready to build a system with VIOS as the Hosting OS and will
be
running several IBM i partitions. I know I should use several smaller
virtual disks vs 1 big one per partition so the IBM i OS wil see multiple
disks/arms. So lets say I have 4 IBM i Partitions all on top of VIOS.
Each
partition will see 8 35GB drives and lets say there are 24 139GB ( or
whatever size VIOS wants to call them ) drives available to VIOS to
allocate
disk space with. So lots of room but could use more arms. Now I start a
really disk intensive process on 2 partitions. How can I tell how busy the
drives really are at the VIOS level? On a partition with IBM i hosting I
can
do WRKDSKSTS on the base IBM i. Just wondering how to approach disk perf
issues inthe future.

Thanks

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Kirk
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