Leopard Server and Virtualization

Tuesday Nov 6th 2007 by John Welch
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In a significant change in direction, Apple has cleared the way for virtualization (as long as you use Apple hardware).

Today, I'm going to start a series of articles on Mac OS X 10.5, "Leopard" Server, but first, I wanted to talk about an announcement that has a great deal of potential for the Mac IT market, namely the change in the EULA (end user license agreement) for Mac OS X 10.5 Server.

As reported by TidBITs, and originally spotted by Dave Schroeder of the University of Wisconsin, Apple made a small, yet quite significant change to the EULA for Mac OS X 10.5 Server. In Mac OS X 10.4 Server the EULA said:

This License allows you to install and use one copy of the Mac OS X Server software (the "Mac OS X Server Software") on a single Apple-labeled computer at a time.
That's pretty clear, and as it stood, meant that neither of the major virtualization vendors on the Mac – Parallels and VMWare – were going to try to release a product that allowed you to run multiple copies of Mac OS X or Mac OS X Server, even on Apple hardware.

However, with Leopard Server, we see this in the EULA:

This License allows you to install and use one copy of the Mac OS X Server software (the "Mac OS X Server Software") on a single Apple-labeled computer. You may also install and use other copies of Mac OS X Server Software on the same Apple-labeled computer, provided that you acquire an individual and valid license from Apple for each of these other copies of Mac OS X Server Software.
That section clears the way to virtualize Mac OS X 10.5 Server on Apple hardware.

Let's be clear about that aspect first, because it has the potential to cause the greatest amount of problems. This is not saying you can virtualize Mac OS X Server and run it on any HP/IBM/Dell/etc. box you may have. It is saying you can run multiple instances of Mac OS X 10.5 Server on the same Apple computer. So this is not going to suddenly allow you to plug Mac OS X 10.5 Server into your ESX farm on Dells.

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(Yes, I know, you can hack it to work, however, you'll get no support, and quite possibly a bit of nasty legal documentation from Apple should they find out. Really, it's not worth the trouble that it would cause on multiple levels.) This change also only applies to Mac OS X 10.5 Server. The client license has not changed to allow this.

So now, what are the positive implications of this? Well, obviously, they are the same as they are for virtualization in general. If you have an Intel Xserve, you will be able to run multiple instances of Mac OS X 10.5 Server on that single Xserve. If you have multiple physical servers that are somewhat underutilized, then you can combine them onto a single Xserve, or possibly a Mac Pro, (interestingly, from a CPU POV, the Mac Pro is a somewhat better choice for a virtualization host, although it lacks the storage and RAM options of the Xserve), and get that same usage out of them, with less HVAC and power used.

Since, in theory, each virtual server is only going to need to run the OS and a small number of applications, you can limit the virtual disk size of the virtual server to a much smaller size than you could do with a physical server, so your overall waste is less. You could also run other virtualized OS's on that Xserve, such as Windows, Linux, Solaris, etc.

For a small, Mac-based company that needs to keep a close watch on costs, and has to run the occasional Windows application on a server, or a small amount of non-Mac OS X applications, this is a great solution. You split your hardware costs over multiple servers. This is a good thing, because you will want to buy the biggest Xserve you can if you're going to have it hosting virtual machines. That means biggest CPU options, all the RAM it can hold, and go with the best combination of RPM and size you can with disk storage. Yes, that's a hefty price, but remember, you're getting 2/3/4/5 servers in one with it. The virtual servers will only require an OS license, so the hardware cost per virtual server can drop pretty quick.

Next page: A fly in the ointment...

A Fly in the Ointment

This brings us to what I see as a bit of a fly in the ointment: Apple Hardware. Right now, even the biggest, baddest Xserve you can buy is at best, a fair to middling virtual server. If this is a market Apple would like to be taken seriously in, then the specs on the Xserve have to come up. Move to an 8-core machine, possibly more. Double the RAM size, etc. Virtual servers may not require their own hardware, but they do require hardware resources. Each virtual machine, or VM, needs a non-zero amount of RAM, CPU, network and disk. If you only have 4 CPU cores to start with, that is going to be a limiting factor in a hurry.

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However, that aside, there are some interesting implications here. Obviously, we can expect to see some product announcements from both Parallels and VMware soon. My question is, will VMware create what amounts to "MacESX"? There are reasons for and against, but I hope the "for" wins out.

On the "for" side, it would allow you to really create an Xserve virtualization "farm" in the same way you do with ESX now. Load balancing, being able to use SAN storage to provide redundancy and hardware failover, fast WAN links to create remote "hot" sites, (I grew up in Florida...a remote hot site there has to be a rather long way away...hurricanes are big), etc. These are things that school districts, higher ed, even the SMB market can all use. True, ESX is actually a "host" OS that runs all the VMs on top of it, but I don't see an actual problem with that for Mac OS X 10.5 Server.

The "against" side for ESX is pretty simple: It would be a bit of an orphan. While you could have a farm of Xserves participating in an ESX cluster, with different OS's, and you could even have them in a cluster with Dells, HPs, what have you, VMware would have to take rather positive steps to ensure that whether accidentally or on purpose, you would never have a Mac OS X 10.5 Server VM running on any physical hardware other than Apple's. I'm not even close to silly enough as to suggest this is easy...or hard for that matter, as I really don't know. I would hope that the people who really want this start bugging VMware now, so that they can see a real advantage to "MacESX".

Virtualization is not a magic spell, even though it seems to be portrayed that way in the computer press. It does not magically make management and other issues go away. It is not the perfect solution for all your server needs, and if you don't have a lot of underutilized boxes, it may not be a good solution for you at all. (Depending on why they're underutilized. If it's because you can't afford more hardware, then it may in fact be a decent option.) However, it is an excellent tool when applied correctly, and Apple allowing for it will help them maintain and grow their market share, especially in the SMB arena.
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