Dear Mr. Sharp
As an IBM i performance consultant, I see that your problem description appears to me as a disk IO throughput limit issue of the SAN disk rather than VIOS issue. But I need more information before I can be sure.
You said you "added an IBMi LPAR with a large 'Read' profile to the SAN . Subsequently both IBMi and AIX I/O response's suffered and we had to move the new IBMi 'read' workload off onto another managed server / SAN to resolve it." In my view, the key information is that all LPARs suffered from (presumably) degraded SAN disk response time .
When this performance issue happened, did you produce a SAN disk performance report (showing disk response time of the disk pool in SAN VS disk IOPS VS disk MB/sec. data rate) and review the disk response time of that SAN box during the period of the performance issue to see whether or not its disk response time degraded for the entire disk pool shared by all those IBM i and AIX LPARs? If so, this issue has nothing to do with having the dual VIOS for all those mixed-OS LPARs but has to do with the SAN disk not being configured to handle the peak total disk IO workload (be it IOPS or MB/sec. or both). If this is the case, you need to enhance the HW configuration of that SAN disk box for a better handling of higher disk workload throughput. This is a case that I encountered a few times in the past few years with my IBM i customers in ASEAN geography who used SAN disk for many LPARs in a Power server.
Just my 2 cents.
Satid S.
IBM Thailand
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SATID SINGKORAPOOM
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Original Message:
Sent: Fri March 12, 2021 06:44 AM
From: Mick Sharp
Subject: Vios I/O Workload Seapration
Hi Norman , thanks for your response that's interesting.
We also have a managed server running both IBMi and AIX LPARS , but using a single dual VIO server setup with HBA port separation on each.This worked fine until we recently upgraded our managed server and migrated our LPARS over, but also adding an IBMi LPAR with a large 'Read' profile to the SAN . Subsequently both IBMi and AIX I/O response's suffered and we had to move the new IBMi 'read' workload off onto another managed server / SAN to resolve it.
Experts involved with resolving the issue were surprised we had this configuration, and have advised at least HBA card separation , if not separate VIOS setups for both.
Are there any definitive rules for new VIO configurations relating to I/O workload best practise , particularly with IBMi & AIX ?
Rgds
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Mick Sharp
Original Message:
Sent: Thu March 11, 2021 09:16 AM
From: Norman Owens
Subject: Vios I/O Workload Seapration
Hi Mick,
We have this setup in our environment. We have IBMi and AIX LPARs running on the same physical managed server. We have a dual VIO server setup for IBMi and a dual VIO server setup for AIX. Each VIO server has a dedicated dual port Fiber Channel adapter assigned to it along with a dual port Network adapter. When we initially setup these VIO servers there was a setting that we were not able to make on the IBMi VIO that we were able to make on the AIX VIO. But over time that limitation was corrected. I think it is a good idea to separate them out like this to ensure that your AIX workload does not affect your IBMi workload. Our IBMi workload does not have as much flexibility as our AIX workload in terms of expectations regarding performance. Hope this helps.
Regards,
Norman Owens
Original Message:
Sent: 3/10/2021 9:53:00 AM
From: Mick Sharp
Subject: Vios I/O Workload Seapration
I would be interested to know your views on separating out IBM i and AIX i/o workloads over multiple vios servers (dedicated to each o/s ) vrs HBA segregation of the i/o traffic on a dual vios server configuration ?
Rgds
Mick
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Mick Sharp
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