Thursday, October 19, 2006

Do Dual Core machines really help when running Virtual Server?

I remember this issue when I had a mighty Rock laptop with a desktop processor and Hyper Threading. Virtual Server can only allocate a single CPU to a guest. Therefore when the guest is CPU bound it is only really getting 50% of the host machine. This is far from ideal! This is made worse by the fact that the absolute clock speed of dual core machines is less than single core machines, which means it is 50% of less.

The mitigation is that when running one guest Virtual Machine the host has a full CPU to service the host, allowing the host to remain very responsive to other activities. The chances are more and more likely now that you will in fact be running more than one VM and therefore all cores will get utilised, but it still doesn't allow one very CPU hungry VM to consume all system CPU resources whilst the others are idle. This can be the case if you have a VM with all the dev tools on and another with all the server products on. When you run a build, the server VM will be mostly idle whilst the dev VM will be very CPU hungry and not able to get as much as it can.

What's the answer - VMWare?...

posted @ 11:26 AM

Dell Latitude 820 - tweaked default BIOS settings for performance and Intel VT

Out of curiosity I interrupted the boot of my new Dell Latitude 820. There were two default factory settings that needed adjusting:

  • Performance - HDD Acoustic Mode:
    1. Bypass (default) - Do nothing (needed for older drives)
    2. Quiet - Slower but quieter
    3. Performance - Faster but possibly noisier
  • POST Behavior - Virtualization: (sic)
    1. Off (default)
    2. Enabled

Clearly I changed the HDD Acoustic Mode to "Performance". This machine is equipped with a 7,200 rpm drive and I am guessing that spinning it slower makes it quieter. The background chatter of a busy HDD doesn't bother me, but hourglasses do!

With Virtual Server 2005 R2 SP1 B2 installed on my machine I had to enable Intel VT support now that Virtual Server will use it.

All in all, two performance options that *should* make my experience better, but I am not going to go through any exhaustive exercise to test the difference! The system is perfectly stable though - which is good news.

posted @ 10:23 AM