RHEL 6.1 KVM Windows XP guest disk IO rate problem

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I have an IBM HX5 blade server pair (2 combined) with a total of 4 50GB solid sate drives.  I have loaded the system using a "standard" LVM configuration and have also tried RAID 0.  After installation of a KVM Windows XP guest, for both types of system OS loads, the guest disk I/O rate is greatly reduced.  I understand that a "virtio" disk should be used to support the para-virtualized drivers but there doesn't seem to be support for this during OS installation.  For the "standard" load, the guest VM disk rate is less than half the host disk rate.  The guest VM disk rate never changes even when a host RAID 0 is used.  Is there anything that can be done to increase this guest disk rate?

Thanks for any help

Jerry

Responses

Hi Gerald,

You actually can install the Paravirt drivers during Windows installation.  Have a look at the RHEL 6 Virtualization Guide for more info:

 

  http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html-single/Virtualization/index.html#form-Virtualization-Installing_the_KVM_Windows_para_virtualized_drivers-Installing_with_a_virtualized_floppy_disk

 

Hope that helps!

 

Regards,

John Ruemker, RHCA

Red Hat Technical Account Manager

Online User Groups Moderator

Hi John,

 

Thanks for your reply.  I actually succeeded today figuring out how to create a Windows XP virtual guest using a "virtio" disk/raw format.  At the start of the guest install, I was able to load the paravirt drivers.  However, once my guest was up and running, I only saw a marginal improvement in the disk I/O rate, which was still around half of what the host disk I/O rate is.  The RHEL 6.1 host is installed on a RAID 0 config.  I'm wondering if better disk I/O would result using no RAID (on the host) and using a block IO device for the guest (instead of using a virtual hard disk file).  Any comments?  Thanks

Hi Gerald,
My experience is that you should notice a slight improvement in performance using a block IO device for the guest rather than a file.