Sunday, February 24, 2008

VMWare ESX 3i 3.5 Speed vs Physical

(Note - Red is Physical Machine with 8 CPUs, Blue is ESX 3i 3.5 with 4 CPUs)

If you're serious about moving to Virtual Servers, you're going to want to know what type of performance hit you're taking for using this technology.

My rough, fairly unscientific results show that using ESX 3i 3.5;

CPU - About 5-10% less than physical

Memory - Nearly physical speed

Disk - Between 50%-75% of physical speed.

Disk takes the largest hit, so you best make sure to follow all the standard ESX "best practices" - Use SAS drives, put Swap on a seperate controller, etc, etc.

Details follow:

I have a new ASUS DSEB-D16/SAS motherboard that I have been running some tests on. So far the speed has ben quite good for ESX 3i 3.5.

My test platform:

- ASUS DSEB-D16/SAS Motherboard

- Two Xeon 2.0 GHz Quad Cores, 45nm

- 8 Gigs ECC Kingston Ram, 667Mhz

- 2 Segate 250 SATAII Drives, set up as Stripe

I've made some tests with Windows 2008 RC1 in both 64 and 32 bit modes, and with Windows 2003 64 bit mode.

I've always used the latest Window drivers for the board and controller.

I used PassMark 6.1 for my testing - It's not overly in depth, but it gives a good overview for what I'm wanting to do.

There is one major messup that I didn't expect - I can only run 4 virtual CPU's in 3i, not the 8 that I have. The first test was with 8 CPUs, and thusly the CPU speed is roughly 50% less in my 3i run. Passmark does make use of every CPU for the CPU portion of the tests (and it runs single CPU for the Memory and Disk mark tests), so this will affect the CPU portion of the tests only.

I have run the test again with only 2 virtual CPUs in 3i, and the results were roughly 50% less than with 4 CPUs. It stands to reason that wil a full 8 CPUs in 3i we'd be very close to the speed of the physical machine.

All my 3i settings are pretty default. I'm going to switch to SAS drives shortly, but I wanted to see the disk test speeds with the existing SATA 250s I used for Windows 2008.

So far, so good. I'm happy with the 3i speed. I can use 32 meg of RAM with my current setup, and it's less than $100 for a 2 Gig stick of ECC 667. I'll keep the RAM high so it's not swapping to disk, and minimize my performance hit on the drives with beefy SAS drives.


  1. Hi there,
    Im running a similar system. ASUS DSEB-D16/SAS, 8gb kingston memory, but using the SAS controller with 5 drives. Ive got ESX 3i running fine on the machine, except for when I power up a VM. It reports the error 'a general system error occurred: internal error'. Did you have to make any bios changes to get your machine working? or was there anything that you did that may have made a difference?

  2. Nope, it's all pretty standard.. some fiddling to get it to boot off the right controller, and I'm using the second BIOS release, but nothing crafty otherwise.