Who's afraid of the VIO?
AnthonyEnglish 270000RKFN Visits (7046)
Who's afraid of the VIO?
Pretty much everybody, at least initially. I can think of two good reasons for that. The first is that your VIO server may have been set up long ago - maybe by someone else when your system was first built. You never touch it. You never need to. It does its magic to provide disk and network traffic for your LPARs and you prefer to leave it alone.
Lost in translation
The second reason is that those familiar with AIX commands find the VIO commands very similar, but different enough to be confusing. Your knowledge of one can cloud your grasp of the other. Like the Italian fellow in a Spanish restaurant who wanted to butter his toast with burro (exhibit 1).
Even those of us for whom AIX is our bread and burro (Italian meaning) found the Virtual I/O server a bit daunting when we first came across it. Sure, it's got a restricted shell with a very limited command set, so it should be easy enough to learn. But the syntax of the VIO server commands (when you log in as padmin) are sufficiently different from AIX that they can be a bit scary.
For example, this command changes a setting on a LUN using MPIO.
chdev -l hdisk0 -a reserved_lock=no
but on the VIO server the syntax is slightly different:
chdev -dev hdisk0 -attr reserved_lock=no
There is also a VIO server command called rmvdev (that's r-m-v-dev, not to be confused with rmdev, which, in turn, has different syntax from the same command on AIX). Tempting for AIX old hats to log in as padmin then go to the full AIX shell (oem_setup_env) and follow the way we know and love.
Proceed with caution
It's a good thing that people are
cautious and even nervous about the VIO server. After all, it's a
central component for disk and network traffic. So yes, it's important that your VIO remains stable, but it's worth being ready if you should ever need to build a new one, rebuild an existing one or just add a new LPAR to your system. The more you steer away from dedicated adapters for your LPARs, the easier your configuration will become, but that does require a bit of leg work getting a grasp of what the VIO is all about.
Let's look briefly at rebuilding the VIO server. Then we can look at where we can go to have a snoop around it. We won't change anything ... just dip our toes in.
Actually, building the VIO server from scratch is easier than doing a new install of an AIX LPAR. The installation of the VIO server is simply a mksysb restore and can be done off the installation media or NIM. Depending on your system configuration, you should be able to have a VIO server up and running in an hour with a vanilla installation.
The VIO server is really about providing devices, so it's really specific to the hardware configuration of the server it's using. If you're cloning to new hardware, for example for a Disaster Recovery
run, you may well prefer to install the VIO server from scratch and build the device mappings yourself rather
than restoring off a backup. If you're restoring to the same physical hardware, you can use the VIOS backup which you hopefully have created using the backupios command or the more recent viosbr command. Chris Gibson shows on his blog how he has used viosbr to backup the VIO server.
VIO for smarties
If you want to get a more high-level understanding of the VIO server and its benefits, check the Virtual I/O (VIO) and Virtualization wiki. It's also got lots of links to valuable documentation. Also, the New Virtualisation Features on the IBM Wiki Movies gives more recent information. You may find movie 52 - VIOS 2.1 Features - particularly helpful.
If you don't have an HMC, then as soon as you install the VIO server you should have access to the Integrated Virtualization Manager (IVM). This is a browser interface to the VIO server which allows you to configure your storage and network via a GUI. See the IVM section on the IBM Wiki Movies.
Since May 2009 the HMC and VIO versions have provided the HMC GUI for VIOS commands. (You may need to bring your HMC up to date first). Although this is slower than the command line, it's probably suitable if you're building a single LPAR or want to do some simple configuration changes.
Whether or not you've got an HMC, you should be able to log in to the VIO server command line and run some basic commands for managing storage or managing networks (via the SEA) on the VIO server. If you're using Active Memory Sharing, you will probably already know about using the VIO server for paging devices.
VIO for dummies
We'll look at the VIO server in more detail on this blog in the future, but for the time being it's worth knowing: