Performance of Virtual machines on very low end machines

virtual-machinesvirtualizationvmware-esxi

I am managing a few cheap servers as my user base isn't large enough to get much more powerful servers. I also don't have the money lying around to invest in a server to prepare for the larger user base. So I'm stuck with the old hardware I have.

I am toying with the idea of virtualizing all the current OS's with most likely VMware vSphere Hypervisor (AKA ESXi) Xen (ESXi has too strict of an HCL, and my hardware is too old). Big reasons for doing so:

  • Ability to upgrade and scale hardware rapidly – This is most likely what I'll be doing as I distribute services, get a bigger server, centralize (electricity bills are horrible), distribute, get a bigger server, etc… Manually doing this by reinstalling the entire OS would be a big pain
  • Safety from me – I've made many rookie mistakes, like doing lots of risky work on a vital production server. With a VM I can just backup the state, work on my machine, test, and revert if necessary. No worries, and no OS reinstallation
  • Safety from other factors – As I scale servers might go down, and a backup VM can instantly be started.
  • Various other reasons.

However the limiting factor here is hardware. And I mean very depressing hardware. The current server's run off of a Pentium 3 and 4, and have 512 MB and 768 MB RAM respectively (RAM can be upgraded soon however).

Is the Virtualization layer small enough to run itself and a Linux OS effectively? Will performance be acceptable (50% CPU overhead for every operation isn't acceptable)? Does it leave enough RAM for the Linux OS? Is this even feasible?

Best Answer

On machines of that age, you will only be able to run very, very old versions of ESX (not ESXi). v2 or thereabouts, if you can find it. And ESX had a footprint of around 128-256Mb around that time, so you won't be able to do much with it when it is installed.

I once had ESX running on a Dual PII 400 with 512Mb of RAM. It wasn't pretty, but no virtualisation was that pretty back then.

You'll also miss out on all the virtualisation technologies that newer processors have.

Personally I would definately go ahead with it (if you can find a copy of ESX that old), but make sure that it's not in production until you're happy with how it performs and its reliability.

What I would definately do is scrounge around until I could afford a bare-bones PC with an i7 processor and a motherboard that is on the VMWare HCL. Depending on where you live in the world, this could range in price from $400 to $1000, and would be worth every cent.

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