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Author Topic: Confused about SDDPCM on VIO?  (Read 7347 times)

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aix_tiger

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Confused about SDDPCM on VIO?
« on: November 21, 2010, 07:42:52 pm »
Guys

I am much confused about possible usage of SDDPCM on my latest VIO server. The VIo server is running latest version of VIOS and backend disk subsystem is DS5100.

Question is that whether i require SDDPCM on VIO server or not? If not , which device driver for DS5100 should i put in VIO server? If i dont put any MPIO driver on my VIOS server , will mutipaths to DS5100 and failover will work?

The confusion arises from following IBM website which says SDDPCM is not supported on VIOS with IBM DS5000 series.

http://www-01.ibm.com/support/docview.wss?rs=540&context=ST52G7&dc=DA400&uid=ssg1S7001350&loc=en_US&cs=utf-8&lang=en#AIXSDDPCM

Please explain!!!

Regards


Michael

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Re: Confused about SDDPCM on VIO?
« Reply #1 on: November 25, 2010, 11:58:24 am »
The short answer is: think of the VIOS as a "pass-through" or "bridging" component for storage. In other words, the VIOS is not really doing the I/O, that is done by the client partition. As such, there is no way for the SDDPCM driver to be effective.

If I recall, you can install it, and it will still function - but there will not be any load balancing being performed when using vSCSI for virtual storage. If you are using NPIV then the VIOS does not even see the disks so no PCM has any real contributition.

vSCSI: AIX MPIO plus manual load-balancing over partitions

NPIV: load SAN PCM software in the VIOC (client virtual machine/client partition) and use "native" SAN drivers and there support - or AIX drivers for the disks.