Virtualizing Cuts Web App Performance 43%

czei writes "This just-released research report, Load Testing a Virtual Web Application, looks at the effects of virtualization on a typical ASP Web application, using VMWare on Linux to host a Windows OS and IIS web server. While virtualizing the server made it easier to manage, the number of users the virtualized Web app could handle dropped by 43%. The article also shows interesting graphs of how hyper-threading affected the performance of IIS." The report urges readers to take this research as a data point. No optimization was done on host or guest OS parameters.

Comments

Bogus Test

[Anonymous Coward]

Who uses VMWare Server in a production environment anyway? We run all of our Web services, Exchange servers and SQL databases in VMWare's Virtual Infrastructure 3. VMWare Player and Server are only ment for lab evironments and low load applications. VMWare even says as much on their website. Either this is just FUD or the author is an idiot. In other news water is wet.

Re:Bogus Test

[Sobrique]

Actually, the company I worked for 6 months back, one of the projects I was involved in was 'VMWare'. Production stuff running on on the ESX servers (which became 'virtual infrastructure') in our datacentre, as a cost effective scalable environment. Yes, we weren't getting 'uber performance' but then again, we were running 150 or so VMs on an 6 server VMWare farm.

One of the other things we prototyped and deployed was 'site services packages' - get GSX (now VMWare Server), stick it on a pair of 2U servers, and attach a storage array to both of them. Then create your 'template' fileserver, DHCP server, print server, proxy, that kind of thing and deploy them to this package. It worked very well indeed - you get a whole new order of magnitude on stability (although to be fair that's in part because we through away the crappy workstations that were doing the 'low intensity' stuff) and was extremely managable, and trivially replacable in the event of a hardware failure.

Performance? No, VMWare isn't that great on performance - whilst it's not bad, in an ideal situation, fundamentally what you are doing is introducing an overhead on your system. And probably contention too. But it's really good at efficient resource utilisation, easy manageability and maintainability.

As an experienced sysadmin, my reaction is screw performance. Let's start with reliable and scalable, and then performance just naturally follows, as does a really high grade service.

Proactive laziness is a fundamental of systems admin. Your job, is essentially to put yourself out of a job - or more specificially, free up your time to play with toys. The best way to do this is build something stable, well documented and easily maintainable. Then your day consists of interesting stuff, punctuated by the odd RTFM when something doesn't work quite right.

Re:Bogus Test

[Bohiti]

Actually, as it's been explained to me, the ESX hypervisor itself is pure proprietary code (and small, too). The Service Console is very readily admitted to be a tweaked out RHEL (3, I believe..). Linux is used to boot, and then (magically?) transfers control of the bare metal to the hypervisor. Linux then jumps into a virtual machine, although it's not presented like a virtual machine, which creates all this confusion.

In the end, the tweaked RHEL that you interact with (ssh, scp) is not the hypervisor, but a VM with special tools that can manipulate the hypervisor.

This is VMware Server and not ESX Server

[Fuyu]

They performed the test on VMware Server not VMware ESX Server which is what most enterprises will use. VMware ESX Server runs on "bare metal", so it does not have the overhead of the host operating system.

Re:This is VMware Server and not ESX Server

[Anonymous Coward]

ESX Server still gives you a base 40% performance hit. I run a ~600 VM farm under VI3 and our performance on Apache fell from 15000 requests/s (mostly static content) to 5000. That was during a load test with one single virtual machine running on the blade. The same load test using IIS went from 13000 to 9000. Also a huge performance hit, although not quite as bad as on Linux. And before anyone says anything, I'm a linux tech and I was somewhat deprssed about the results, to our windows techs great joy.

Re:Not a trusted source

[dagenum]

The hyperthreaded capacity was actually 390 so a 3% gain.

Re:single data point is correct

[TheRaven64]

The biggest overhead from most forms of virtualisation is from emulated devices. If you have loads of money, you can give it to IBM and get some hardware with virtualisation-aware network and block device controllers. Then you get good performance. Alternatively, you can use paravirtualised device drivers. Xen supports this by default, and I think KVM does now for networks. Not sure about VMWare.

With paravirtualised devices, or devices that are virtualisation-aware, a VM can be within 10% of the performance of a real machine quite easily. Without I'm surprised they even got to 57% of native performance for web applications.

Re:Pointless test?

[LurkerXXX]

No it's not insane. Lots of customers want full root access on their systems so they can install whatever they want (different database or other servers, or even alternate OS's). Virtualization is the only way to go for that.

Re:Pointless test?

[GiMP]

AssignUserId only works with the perchild MPM, which has the following caveat: "This module is not functional. Development of this module is not complete and is not currently active. Do not use perchild unless you are a programmer willing to help fix it."

Thus, AssignUserId should NOT be used. SuExec can be used, of course, but that has its own limitations.

Personally, I give users their own Apache processes on their own port (>1024) and use a reverse proxy. I make a living on it.

Re:Pointless test?

[Just Some Guy]

You run virtualised web servers because 99.9% of all web servers are idle at any given time. So you put 100 on a server.

If you have a real need to run 100 separate Apache instances, then you'll want something much higher-level than VMWare. For us, that would be a FreeBSD jail, where each instance would get its own chrooted home directory and IP address. That way, you're not allocating resources to 100 little-used OS images; each shares from the same memory and hard drive pool. Jails are slightly limited in that I'd like a way to limit CPU and memory allocation, but in practical application this really works very well today.