FreeBSD 7.1 disk performance issue on ESXi 3.5

Ivan Voras ivoras at
Tue Feb 10 06:05:10 PST 2009

Sebastiaan van Erk wrote:
> Hi,
> I want to deploy a production FreeBSD web site (database cluster, apache
> cluster, ip failover using carp, etc.), however I'm experiencing painful
> disk I/O throughput problems which currently does not make the above
> project viable. I've done some rudimentary benchmarking of two
> identically configured virtual machines (2 VCPUs, 512MB memory, 8GB
> disk) and installed one with FreeBSD 7.1-amd64 and one with Linux Ubuntu
> 8.10-amd64. These are the results I'm getting with dbench <n>:
> <n>             1               2               4
> freebsd         12.0009         13.6348         12.9402         (MB/s)
> linux           376.145         651.314         634.649         (MB/s)
> Both virtual machines run dbench 3.04 and the results are extremely
> stable over repeated runs.
> The virtual hardware detected by the FreeBSD machine is as follows:

> Does anybody know how I can get proper performance for the drive under
> ESXi?

VMWare has many optimizations for Linux that are not used with FreeBSD.
VMI, for example, makes the Linux guest paravirtualized, and then there
are special drivers for networking, its vmotion driver (this one
probably doesn't contribute to performance much), etc. and Linux is in
any case much better tested and supported.

If VMWare allows, you may try changing the type of the controller (I
don't know about ESXi but VMWare Server supports LSI or Buslogic SCSI
emulation) or switch to ATA emulation and try again.

A generic optimization is to reduce kern.hz to something like 50 but it
probably won't help your disk performance.

As for unixbench, you need to examine and compare each microbenchmark
result individually before drawing a conclusion.

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