A few months back I wrote about IBM i and VIO server, so I was immediately intrigued when a colleague recently pointed me to this document on IBM i virtualization and open storage. I believe this is an updated version of the original. Take the time to give it a read.
Here's some more good information on IBM i. This document is
called the performance capabilities reference:
"The purpose of this document is to help provide guidance in terms of IBM i operating system performance, capacity planning information, and tips to obtain optimal performance on IBM i operating system."
I found this pretty interesting. Some of it feels very conservative to me compared what I see in the AIX world. If I wasn't familiar with VIOS and its benefits, reading this document would honestly make me a bit reluctant to use it in production with IBM i. Despite this -- and the fact that this document is intended for IBM i users -- I think AIX pros can also benefit from the information. We have Power Systems hardware in common, after all.
Some quick highlights:
* Chapter 2 covers IBM i communications performance.
* Chapter 4 covers internal storage performance. Page 35 has a good chart comparing SSD, SAS and SCSI disk, controllers and enclosures. Here's one example of information that should interest AIX users. Though the numbers might not match exactly, we can still gain good information here.
* Chapter 5 has details on SAN performance numbers, while chapter 6 covers VIOS and IVM. Section 6.2.2 should give you perspective on why IBM i users would find it scary to move to external storage. Their storage has always been managed internally, going back to the introduction of the AS/400 systems. Now these folks have to trust SAN admins to RAID-protect their disks, and even if the disk is protected, IBM i will report otherwise.
* Section 6.2.3 reminds you to not put LUNs into volume groups when using VIOS.
Simply map the LUN directly to the client LPAR. Also remember that with IBM i,
you can only have 16 virtual disks on each virtual SCSI adapter.
* Section 6.4 provides examples of virtual SCSI performance. Section 6.7 has a VIO client performance guide, while section 6.8 gives performance observations and tips.* Chapter 7 covers logical partitions and best practices when setting them up. There's good information about applications running on IBM i, and at the end check out chapter 19 for general performance information tips and techniques. This material is pretty specific to IBM i, however.
Given the audience for this blog, I don't often write about IBM i. But I do so occasionally, because I believe it's worthwhile. Tempting as it might be, AIX pros shouldn't dismiss this topic. It's that sort of mentality, after all, that's kept IBM i admins from embracing VIOS. ("VIOS is so much like AIX. Why should I bother with it?")
Perhaps 15-20 years ago, that attitude would be acceptable. But, again, we all use the same hardware now. In some environments today, AIX and IBM i run together on the same physical frame. Knowing where everyone is coming from -- especially as it pertains to a vital area like system performance -- can be very beneficial.