VIOS and IBM i

Edit: Some links no longer work.

Originally posted March 27, 2012 on AIXchange

Two questions for IBM i shops: Are you reluctant to use a VIO server and attach it to your SAN, even though your SAN isn’t supported directly by IBM i? Do you end up telling yourself that internal disks give you better performance?

If so, this document might help alleviate your fears.

It covers different topics related to IBM i virtualization and open storage, including how to use an IBM i partition to host another IBM i partition:

“An IBM i 6.1/7.1 LPAR can host one or more additional IBM i LPARs, known as virtual client LPARs. Virtual client partitions typically have no physical I/O hardware assigned and instead leverage virtual I/O resources from the host IBM i partition. The types of hardware resources that can be virtualized by the host LPAR are disk, tape, optical and networking.”

There’s also this about IBM i using open storage as a client of the VIOS:

“IBM i virtual client partitions can also be hosted by VIOS. VIOS is virtualization software that runs in a separate partition with the purpose to provide virtual storage, optical, tape and networking resources to one or more client partitions. The most immediate benefit that VIOS brings to an IBM i client partition is the ability to expand its storage portfolio to use 512-byte/sector open storage. Open storage volumes (or logical units, LUNs) are physically attached to VIOS through a FC or a Serial-attached SCSI (SAS) connection and then made available to IBM i. While IBM i does not directly attach to the storage area network (SAN) in this case, as soon as open storage LUNs become available through VIOS, they are managed the same way as integrated disks or LUNs from a directly attached storage system and run IBM i on a Power blade.”

Finally, something about blades:

“The third major virtualization enhancement with IBM i 6.1 is the ability to run an IBM i LPAR and its applications on a Power blade server, such as IBM BladeCenter JS12 or JS22. Running IBM i on a Power blade is beyond the scope of this paper. Refer to the IBM i on a Power Blade Readme First for a complete technical overview and implementation instructions.”

The document covers supported configurations and concepts to help you visualize what I’m proposing. I’ll highlight this section on 5.2 performance:

“When creating an open storage LUN configuration for IBM i as a client of VIOS, it is crucial to plan for both capacity and performance. As LUNs are virtualized for IBM i by VIOS instead of being directly connected it may seem that the virtualization layer will necessarily add a significant performance overhead. However, internal IBM performance tests clearly show that the VIOS layer adds a negligible amount of overhead to each I/O operation. Instead, the tests demonstrate that when IBM i uses open storage LUNs virtualized by VIOS, performance is almost entirely determined by the physical and logical configuration of the storage subsystem.

“The IBM Rochester, MN, performance team has run a significant number of tests with IBM i as a client of VIOS using open storage. The resulting recommendations on configuring both the open storage and VIOS are available in the latest Performance Capabilities Reference manual (PCRM).”

I find more customers that are willing to give VIOS a try. I’ve yet to find one that decided to switch back because performance was unacceptable.

I realize that this blog’s readership is very AIX-centric, but plenty of shops run Linux and IBM i as well. It’s nice to know that the frame that you’re virtualizing with VIOS to run AIX can run other operating systems as well. Not that this is a new idea.