philipnet

I was looking for a few documents on VMWare performance.

I’ve recently had the notion of building myself a meaty server running Linux (Ubuntu) on which I can run test servers/desktops as much as I want. It saves running them on multiple 500MHz PIIIs which I can get cheap on eBay .

I wanted to confirm something I read on how to setup VMWare on Linux (Ubuntu) which was to configure the Guest OS with a SCSI hard drive rather than an IDE one.

So I went search for VMWare Performance docs; and found a few useful URLs:

1. Performance Tuning Best Practices for ESX Server 3 http://www.vmware.com/pdf/vi_performance_tuning.pdf
   Which details various things to ensure to get the best performance out of your VMWare server and the Guest OSes.
2. Storage Subsystem Performance in VMware ESX Server: BusLogic Versus LSI Logic http://www.vmware.com/pdf/ESX2_Storage_Performance.pdf
   Which details the speed comparison of two SCSI drivers(!)

So I’m no where near where I wanted to be. So let’s try the VMWare site; and I find the GSX manual http://www.vmware.com/pdf/gsx32vm_manual.pdf which tells me:

“The wizard recommends whether to use SCSI or IDE, based on the guest operating system installed in the virtual machine”

Some help that is! I want the answer now!

So back to Google it is and on the VMWare site I find the text:

“The maximum size is 128GB for an IDE virtual disk or 256GB for a SCSI”

So I’m getting closer. And then I find this post (and I’m about to give up!):

IDE vs SCSI under Virtual Server http://blogs.msdn.com/virtual_pc_guy/archive/2006/02/06/525487.aspx

“The final thing to consider is performance - and this is a bit tricky.  Contrary to common sense, the performance of our emulated SCSI controller is slower than that of our emulated IDE controller.  The reason for this is that the SCSI controller is a lot more complicated to emulate than the IDE controller.  Now - this changes once you have Virtual Machine Additions installed.  As part of Virtual Machine Additions we install an accelerated SCSI driver.  Once this driver is installed the performance of our emulated SCSI controller is significantly faster than our emulated IDE controller.”

Okay, so it’s the wrong software, but right camp. So one final Google later I find this forum posting:

Choosing SCSI vs. IDE for boot drive 
http://www.vmware.com/community/thread.jspa?messageID=83153

“After I failed to find DOS drivers that would let my Ghost boot disk see the SCSI boot drive, I recreated the VM with an IDE drive and all my problems went away.”
…
“Do you plan to migrate the VM to ESX at any time? If so, then you should use SCSI since ESX does not support IDE disks.”
…
“If your guest OS includes "more intelligent" SCSI drivers, then you may get better performance from a SCSI virtual disk than from an IDE virtual disk.”

So; concrete answer may be none, but the answer is there. Go IDE if you want a quite life, or go SCSI and install the VMWare Tools CD.