Re: VIOS and Perf Monitoring

[Kirk Goins <kirkgoins@xxxxxxxxx>]

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
>
> --
> Kirk
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