Tech: Better timekeeping in VMware ESX Server 3.0

Richard Garsthagen, Technical Marketing Manager at VMware, published on his blog details about a new experimental feature introduced with ESX Server 3.0: the Descheduler Time Accounting (DTA) service.

This service, which has to be installed with a custom setup and has to be manually activated, is an attempt to better control how time is calculated in virtual machines.

The most important point is not the service in itself but the fact erroneous time management impacts on virtualization benchmarks:

Having proper time reporting in a Virtual Machine as always been a challange and there are many ways to solve this. You can use the buildin Time Sync from VMware Tools or use things like Active Directory or NTP. For most applications this works fine, but if you want to run things like benchmark tools this is not sufficient. The more a Virtual Machine get stressed, the worse it’s time sync will go…

Read the whole article at source.

The fact VMware is trying to mitigate issues in performance measurements isn’t a surprise: the company is expected to announce a benchmarking system, dubbed VMmark, at VMworld 2006, in November.

But if time calculation impacts so much on benchmarks then a question raises: assuming every vendor is handling time in its virtualization platform in different ways, how VMmark or any other benchmarking system could really compare performances of different products’ virtual machines?