So, you just got off a call with an IBM salesperson who’s convinced you that Virtual I/O Server (VIOS) is the only way to virtualize on Power Systems. You’ve been fed a load of nonsense about how VIOS is essential for performance, mobility, and resilience. But here’s the truth: for most AIX users, Workload Partitions (WPARs) are simpler, cheaper, and just as capable. This page will break it down, clear up the misconceptions, and show you why you don’t need to buy into the VIOS hype.

WPARs (Workload Partitions): A built-in AIX feature that lets you create isolated, lightweight environments within a single AIX instance. They share the AIX kernel, so they’re fast and efficient.

VIOS (Virtual I/O Server): A separate partition that virtualizes I/O resources (think network and storage) for multiple Logical Partitions (LPARs). It’s part of PowerVM and supports AIX, IBM i, and Linux.

VIOS sounds fancy, but if you’re running AIX-only workloads (like most Power Systems users), it’s usually just a cost-cow and a complexity sink. Let’s dig into why.

There’s one scenario where VIOS actually makes sense: You’re running multiple OS types (AIX, IBM i, and Linux) on a single Power System.

You’ve got a limited number of I/O adapters and need to share them across multiple LPARs.

Here, VIOS acts like a traffic cop, virtualizing I/O so all those LPARs can share the same physical hardware. Cool, right? Except this is an edge case. Most AIX shops don’t mix OS types, and even if you do, modern Power Systems often come with enough physical I/O adapters to avoid this hassle. If you’re not in this super rare fantasy-boat, VIOS is just extra baggage—expensive baggage.

So, how many customers do you think mix AIX, OS/400, and POWER Linux on the same physical server? I've worked with POWER systems since 1993 and I've never even seen one who did anything close to that. That's the big sell? Pfft, no way that's realistic in the slightest.

For AIX-only setups, WPARs beat VIOS hands down. Here’s why: Cost: WPARs come free with AIX. Mobility features need a license, but it’s still way cheaper than VIOS’s per-core pricing.

Simplicity: You manage WPARs with familiar AIX tools like mkwpar or SMIT. No Hardware Management Console (HMC) or clunky padmin interface required.

Performance: WPARs share the AIX kernel, so there’s less overhead than VIOS’s full-blown LPAR approach.

Mobility: With the Mobility feature (yes, it’s an add-on), WPARs can move between LPARs or systems without downtime—same as VIOS’s Live Partition Mobility.

WPARs handle isolation, resource management, and mobility with less fuss and no extra cost. So why did that salesperson push VIOS so hard? Let’s tackle those misconceptions next.

VIOS is not a panacea for AIX. Let's start with the fact that it's not AIX at all! IBM modified AIX heavily to make sure the trusted commands you use and your old ways of fixing things absolutely won't work in VIOS. Think about that. They had to take AIX and change the name of dozens of commands to make sure your skills would not apply and you'd be scared straight into buying platinum support. They put their customers at a disadvantage simply so they could benefit.

Then there is the cost. Most folks figure about $1000/core for VIOS licenses. That's insane in terms of cost, especially compared to just running AIX using WPARs without VIOS. Even if you purchase the “mobility” features (which do cost $$$) for AIX WPARs, the costs are much lower. So, why pay more for something that's going to cause you more headaches in the long run?

VIOS is a big black box. Pretty much none of it is accessible by mere mortal sysadmins. Almost all the time, issues aren't corrected with customer education, they are fixed with patches. Now, IBM is saying they will custom encrypt the VIOS patches so they will only install frame-by-frame on existing entitled customers. So, forget getting one set of patches to apply to your whole farm. In my experience, VIOS fixes are almost all like this: binary blob black boxes responding to APAR bugs.

Upgrading VIOS is a white knuckled terror. Yes, you might have dual VIO servers in case one fails, but can you clone and rebuild them at will? No? Because you're going to need to do that if one of them cannot be restarted after patching or upgrading it. VIOS patches are big binary blobs that have a pretty janky patch system. Betting the farm is going to stay up while you upgrade is not a fun experience. That's like having to take your operating budget to the casino and bet on Red or Black every time you run low on cash. It's not a great strategy.

Lastly, VIOS support isn't very well staffed. We hear a lot of complaints (and I've seen it first hand myself) that IBM tends to miss it's SLAs on getting someone who knows VIOS to call you back. Why? Because they offshored all their support to India and very little of this stuff was engineered in India. They don't eat their own dog food. They don't have adequate support staff or they fail to manage them correctly, or we wouldn't see folks with a two hour SLA waiting six hours to get a technician.

You’ve probably heard some of these lines from IBM: “VIOS is the only way to virtualize.” Wrong. WPARs virtualize workloads within AIX—no VIOS needed.

“VIOS is faster.” Nope. WPARs have lower overhead because they skip the extra virtualization layer VIOS adds.

“Mobility requires VIOS.” False. WPARs’ Mobility feature does the job just fine.

“VIOS is more resilient.” Not really. On one system, VIOS’s dual-LPAR trick doesn’t save you from hardware failures any better than AIX’s built-in multipathing and mirroring.

The salesperson might’ve dazzled you with VIOS’s bells and whistles, but for AIX workloads, WPARs deliver without the complexity or price tag.

Still not convinced? Check out this matrix:

See that? WPARs match VIOS on almost everything that matters for AIX—except I/O virtualization, which you probably don’t need. Yes, VIOS has slick GUI tools via the HMC, but here’s the kicker: the WPAR Manager GUI is likely still available. Why? Because IBM still sells the Mobility license. They wouldn’t keep that around without supporting the tools to manage it, right?

Unless you’re juggling multiple OS types with scarce I/O adapters, VIOS is overkill. WPARs give you the same core benefits—virtualization, mobility, resource control—for less money and headache. Don’t let the IBM salesperson’s pitch fool you into buying something you don’t need. Stick with WPARs, and you’ll keep your AIX environment lean, mean, and cost-effective.