Disk access/MPT under ESX3.5

[Clifton Royston]

On Sun, May 18, 2008 at 04:15:55PM +0200, Daniel Ponticello wrote:
> Hello,
> i'm running some tests with FreeBSD6.3 and FreeBSD7-Stable, using both 
> AMD64 and I386 arch
> with both schedulers (ULE and 4BSD) on VmWare ESX3.5 server.
> Everything runs almost fine, except for disk access. Performance is 
> quite OK (around 60mb/sec),
> but when accessing disks, System (kernel) CPU load goes up to 70%. This 
> doesn't look
> normal. The same behavior is present on all test configurations.
...
> da0 at mpt0 bus 0 target 0 lun 0
> da0: <VMware Virtual disk 1.0> Fixed Direct Access SCSI-2 device
> da0: 3.300MB/s transfers
> da0: Command Queueing Enabled
> da0: 34816MB (71303168 512 byte sectors: 255H 63S/T 4438C)
>
> Any suggestions?

If you are accessing a software emulation of a SCSI disk, I would
offhand expect the CPU load to go up substantially when you are reading
or writing it at the maximum achievable bandwidth.  You can't expect
normal relative load results under an emulator, and while most
application or kernel code runs natively, I/O under VMWare will zoom in
and out of the emulator a lot.  I'm afraid I can't give you a
definitive answer as I have VMWare but haven't set up FreeBSD under it
yet.
 
  -- Clifton

-- 
    Clifton Royston  --  cliftonr at iandicomputing.com / cliftonr at lava.net
       President  - I and I Computing * http://www.iandicomputing.com/
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