An Overview of Virtualization Technologies

PCM2 writes "Virtualization is all the rage these days. All the major Linux players are getting into the game with support for Xen, while Sun has Solaris Containers, Microsoft has Virtual PC, and VMware arguably leads the whole market with its high end tools. Even AMD and Intel are jumping onto the bandwagon. InfoWorld is running a special report on virtualization that gives an overview of all these options and more. Is it just a trend, or will server virtualization be the way to go in the near future?"

No Mention of UML

[Zane Hopkins]

They completely forget to mention User Mode Linux, which is a well established and stable linux only offering, and many of the VPS (virtual private server) hosts you see advertised are running on UML.

It seems that as Xen makes progress, UML is getting ignored.

Re:Mainly a cure for bad software

[Detritus]

Dependencies. Package A is tested and certified to run with Foo 1.5 and Bar 2.0. Package B is tested and certified to run with Foo 2.0 and Bar 2.1.

Re:And IBM? Where are they?

[joe90]

They talk about VMWare, Intel/AMD, the future Solaris on E10000, other things... but where is IBM?

Since IBM practically invented virtualisation in the '60's for their mainframes (or possibly earlier (I'm not quite that old), I was quite surprised to see it missing from the Infoworld articles too.

IIRC, VMWare modelled their solution on IBM's implementation. They may have also licensed some of the technology to do it.

Don't forget Linux Vserver

[caluml]

Don't forget Linux-vserver [linux-vserver.org] - it's very good, and very fast - as root in a vserver is root on the actual host - processes just can't "see" or kill any outside their own context. Props to Bertl.

Re:No Mention of UML

[arivanov]

I host my website and mailservers at Memset [memset.com] which was one of the first to offer large scale UML hosting. They have now switched almost completely to Xen. I have seen the same happening elsewhere as well. UML is being forgotten despite being a better overall idea which is quite sad.

Re:Just a trend? NO WAY

[Anonymous Coward]

Secondly, just think of the possibility to move server images from a physical server to another one, literally freezing it here and awakening it over there - InstaScaleOut(tm) must be a server admin's wet dream. Well, you'll poo your pants when you see vMotion in work, then. the ability to move a running VM from one host server to another without a hitch is quite something. Combine that with Resource Pools, DRS and HA and suddenly the hardware doesn't matter so much anymore!

Consolidate Costs .

[straybullets]

If you stat average CPU consumption over the servers of any big size datacenter chances are you will be very surprised by the results.

I did this for a company with over 2000 unix servers and averages were : only 20% of the hosts would use more than 30% of the CPU ...

It's a known fact that for most of the projects the hardware is super sized over what's really needed, and this is one of the main advantage of virtualization : it is seen as a cost reduction process.

Re:Way too long of a FA, and not exactly accurate.

[Znork]

"Migration only takes a few seconds once that's done .."

An interesting way to accomplish file-based fast migration is to nfs mount an area on the target server, then use md (in the virtual machine) to place a mirror there. Then you have no need for the lengthy copy, you already have a synced up online copy there.

Not saying it's good, just saying it works (and a useful alternative if you dont have a better shared storage) :).

Re:Way too long of a FA, and not exactly accurate.

[tinkertim]

Sorry for the double bang, I forgot to comment on the author mentioning Migrating NetBSD dom-u's using the loop-n-go method.

You can't mount bsd slices as a loop device. You need a utility like lomount. Here's a copy [netkinetics.net] if you read the article and want to play with Xen/NetBSD. Compiles easily with gcc.

Just another example of how you can frustrate people with mis-information, and give the topic of your article the bad rep.. when it was really a lack of research on your part.

Cheers :)

Re:Mainly a cure for bad software

[jcurran]

Also, it solves the need for a straightforward rollback mechanism when upgrading windows for application X and finding breakage in this week's MS patch set... Take an image snapshot, patch, test, and simply revert by selecting the prior image. Expect to see more systems running under VM for this and security rollback purposes.

IBM == GODS OF VIRTUALIZATION

[Anonymous Coward]

IBM is so far advanced it's not even funny.

Intel and Xen even based their virtualization stuff on old papers from IBM documentation and whitepapers.

You want to know how hardcore IBM is?
THEY INVENTED VIRTUAL MEMORY. And no I am not talking about a swap file on your harddrive, you windows wennie. I am talking about the ability every PC has to abstract memory.. It's IBM's gift to the PC that made modern computing possible.

You aren't convinced of IBM's monsterious power?
They have it setup so that when you buy a OpenPOWER machine for running Linux you can get a optional firmware hypervisor to manage multiple operating systems. And it's pretty cheap also.. For the same price as a low end Sun Opteron box you can get a low end IBM POWER5 box.

But it's not just that... Get this:
IF you buy a Xeon cpu on a add-on card you can set up the machine to RUN WINDOWS.

That's right. Run windows with a fucking x86 cpu on a PCI CARD.. Sharing the same memory and harddrives as Linux running on POWER5. On the same machine. At the same time. With NO slowdown.

Still not convinced?
How about this, for a show of IBM's utter superiority in this feild:
We are running a 2000 era IBM Mainframe with a late 1970's operating system on a 1990's operating system with 1980's era tape drives for legacy reasons.

IT'S A THIRTY-ONE BIT (no NOT 32 bits. 31bits.) OPERATING SYSTEM ON A #$%#$% 64 BIT MACHINE. It's not even like going from x86 to x86-64. They are entirely different computer archatectures. AND it runs at near bare hardware speeds. It's incredable. AND we can run Linux next to it. At the same time. And not just one Linux install, but very literally hundreds of them if we felt like it.

It's completely nuts. They got shit that makes Vmware look like Dosbox. Microsoft's 'Virtual Server' isn't even on the radar; it's completely laughable in comparision.

That and it has the worst possible user interface imaginable. Think about the worst thing you've ever seen. Some DOS 2.x nightmare. Now add a OS/2 GUI and make it WORSE. Now imagine it worse then that. Now your getting close. That and we pay out the ass for the pleasure of using it. Ok, now make it slightly worse. That's about right.

The other end of virtualisation

[AmunRa]

I see no mention of virtualisation techiques that virtualise a different architecture - such as Transitive's [transitive.com] QuickTransit software, of Rosetta fame. They announced a version of their software the other day which virtualises a SPARC Solaris machine on x86-64 Linux, which sounds more interesting than simply pretending to be yourself :)

Re:IBM == GODS OF VIRTUALIZATION

[DaKrzyGuy]

The mainframe was originally 24-bit..who ever would need more than 16MB of memory?? Well sometime in the 70's they realized they would need more...so they extended the architecture but used bit 32 of the address field to tell if it was in 24 or 31-bit mode. They have since added a 64-bit mode with their z-Architecture in 2000. They are all still natively supported in hardware...

Re:IBM == GODS OF VIRTUALIZATION

[GooberToo]

Most people don't realize that many moons ago, some CPUs had really odd bit sizes...like 7-bit bytes, 31-bit ints, etc...etc...I forgot the odd reason why this sometimes happened...but those odd beasts really did exist...I'm surprised someone is still running an OS based on these odd balls.

Re:IBM == GODS OF VIRTUALIZATION

[Anonymous Coward]

You got to lay off the crack there buddy.... yeah IBM is the pioneer in virtualization, but they are lagging behind the new comers.

For example, IBM cannot currently migrate a running LPAR. In the next iteration of their technology they say they will be able to do that, but not now.

For the same price as a low end Sun Opteron box you can get a low end IBM POWER5 box.

The lowest priced POWER5 is the p505, which lists for $3,399. The lowest end Sun Opteron is priced at $745. At that baseline price of $3,399 you get the basic hardware. What you don't get is an AIX license. You don't get APV. You don't get an HMC. You don't really get much in the way of virtualization capabilities at all. You'd use a system like that for your developers to use as a test platform. Maybe a webserver or a light weight application server. And for those tasks you'd be better off buying x86 based kit and running Linux, Solaris, or one of the BSDs.

Don't ever start arguing IBM v. anybody on the price battlefield, IBM loses everytime. Our shop is migrating onto IBM for one of our applications. We worked with the local IBM reps to get a system to have so we could all come up to speed. This beginner system (p550) with low-end options, that the sales guy claimed to be giving to us, cost over six figures.

Re:Just a trend? NO WAY

[GoRK]

I am not an expert with Server (GSX) -- I mainly stick to ESX. I do; however run some VMware Server machines in the lab and know what you are talking about -- this symptom sounds like a memory management issue. I'd bet dollars to donuts that your guest is getting partially swapped out either because you have given the guest more memory than it really needs (this is a very common problem), you have not configured the host to prevent swapping ("Fit all virtual machine memory into reserved host RAM" under "Host Settings" in the server console), you do not have enough ram in the machine to allocate enough to the guest (and the guest is swapping itself out), or you are running services on the host machine that are dragging down the guests. You have to remember that even though VMWare Server lets you oversubscribe your system RAM, it is up to you NOT to do it. Unlike ESX, VMware Server does not have the ability to share identical memory pages among VM's, thus oversubscribing memory in Server although possible is never a good idea. In ESX, however, memory subscritption is probably the biggest advantage VMware has over any other solution at this point.

If you are using VMWare Server, please keep in mind that best practices say that you should generally NOT RUN SERVICES ON THE HOST ! It is far better to minimize the footprint of the host and create another VM to handle the services instead. There are of course exceptions to this such as when an application needs physical access to hardware that VMware can not supply or emulate, but they are not common.

If this doesn't help you, please check the VMTN forums for help; they have a points system for questions/answers and are generally one of the better free support forums for any commercial product I have ever seen.

No notice of IBM Virtualization on pSeries?

[acorliss]

Hard to believe that they wrote an article that even mentioned virtualization on mainframes, and didn't think to mention IBM's pSeries solution with runs both AIX & Linux. I ended up going that route over blade servers because it was simply cheaper to implement without sacrificing hardware robustness and redundancy. Not to mention the flexibility of a SAN-backed server....

cheaper, too

[sethg]

I recently switched my mail/Web server from a G4 running in my basement to a virtual machine at OpenHosting [openhosting.com]. Previously, I was paying $70/month for DSL with a static IP address; now I pay $20/month for OpenHosting and $15/month for DSL without static IP. And I have someplace off-site to back things up to, and I don't have to worry about the UPS battery running out or the disk drive going kablooey.

The only downside is that my basement server runs Debian and OpenHosting runs Fedora. But nobody's perfect. :-)

Works well for license servers

[caseih]

Virtualization has been great for dealing with pesky license servers. Some very expensive software packages require a license server that talks to a hardware dongle. In a university setting, we sometimes run dozens of these license servers. Even worse, most license managers expect the dongle to always be on parallel port one. So with vmware server, we can set up a bunch of dongles on an expansion card, then map each port into the vmware image. Furthermore, each vmware image can have a particular mac address set for it, so even if we have to change hardware or move the license server image around, everything stays set. Dongles are evil. But virtualization makes it liveable. And prevents us from having to have dozens of separate machines that do nothing by run the license software.