FreeBSD 7.1 disk performance issue on ESXi 3.5

Ivan Voras ivoras at
Wed Feb 11 02:12:41 PST 2009

Antony Mawer wrote:
> Ivan Voras wrote:
>> Sebastiaan van Erk wrote:
>>> Sebastiaan van Erk wrote:
>>>> (However, just to give you an idea I attached the basic 5.1.2
>>>> unixbench outputs (the CPU info for FreeBSD is "fake", since unixbench
>>>> does a cat /proc/cpuinfo, so I removed the /proc/ part and copied the
>>>> output under linux to the "procinfo" file.)
> ... benchmark results snipped ...
>> The results are ... interesting. It seems that FreeBSD simply dies in
>> any test having a high context switch rate. Hmmm, this looks familiar.
>> Either I or a collegue of mine had a similar situation some time ago,
>> with the same discrepancy in disk speeds and the same difference in
>> context switches. Unfortunately, there was no solution.
> How would one go about gathering data on such a scenario to help improve
> this? We were planning a project involving VMware deployments with
> FreeBSD 7.1 systems in the near future, but if performance is that bad
> it is likely to be a show stopper.
> Where do we start looking and who should we be talking to?

Relax, we didn't yet actually establish that it isn't a local problem.
I've talked a little with OP but nothing we did yet made it better.

For what it's worth, my experience is that on VMWare Server, whose
emulated SCSI hardware is detected exactly the same as on ESX, the
performance is "normal" (i.e. as expected), and on an ESX 3.0 on a slow
array (and sharing it with other active machines) I get results around
20 MB/s in dbench - which is better than the OP gets on a fast array.
All this is with 32-bit guests, FreeBSD 7.0 or 7.1.

If I get the chance, I'll try ESXi within the next few days and try to
replicate the problem.

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