NT4 Guest: IDE vs SCSI

[_Royce_]

Everything I've read says that SCSI should perform better, but my benchmarks using microsoft's SQLIO utility show otherwise.

I see significantly better performance using IDE.

For a database server, I'm wondering whether SCSI would be better for avoiding bottlenecks when the number of concurrent database users increases.

What am I missing?

[continuum]

I remember a time -maybe 7 or 8 years ago when the same issue surprised many users. We all recommended IDE over SCSI then.
If I remember right that strange effect only affected NT 4.
So dont think your benchmarks were incorrect - years ago lots of users were surprised when they noticed that IDE.vmdks outperformed buslogic scsi - and also were more stable.
Only thing that surprises me now is that this still is the same for latest WS versions,

I would just keep the IDE vmdks as they are  - changing back to scsi does not make sense to me,
I would also recommend to switch to IDE for VMs that use a database .

[_Royce_ · Accepted solution]

Well interestingly enough I believe the issue was poor benchmarking from the tool I was using.

I did some alternate benchmarking:

• Duplicate large file on same drive
• Use CrystalDisk Mark

The file duplication test, which is both reading and writing to the same drive concurrently, showed substantial speed improvement with BusLogic SCSI.

Crystal Disk Mark results also showed substantial performance gains with SCSI.

BTW, for anyone interested, I initially struggled with the conversion of controller types with a VMDK, but it's actually really simple.

You don't need to edit the .vmdk file as suggested by the VMware KB (this usually ends up in an unusable VMDK).

You use qemu-img.

Example: IDE to BusLogic SCSI

qemu-img convert input.vmdk -O vmdk output.vmdk -o adapter_type=buslogic

Then remove the IDE disk and add a SCSI disk for the converted file in your VM settings.

Don't forget to install the SCSI buslogic driver beforehand so that when you boot the VM, the new SCSI disk can be read.

To see all the different conversion options with qemu-img, use this:

qemu-img convert input.vmdk -O vmdk output.vmdk -o ?

qemu-img is awesome.

[roozgar]

Don't forget to install the SCSI buslogic driver beforehand so that when you boot the VM, the new SCSI disk can be read.

how can i install scsi driver? i changed my hard disk to lsilogic but diont boot up