Solution: KVM guest IO very slow

One problem of virtual server based on qemu KVM is that IO operations are slow in some cases.

The most common reason is that virtual disks are stored on RAID and virtual is using default HDD configuration.

It is recommended to turn off cache and set io operations to native:

<driver name='qemu' type='raw' cache='none' io='native'/>

There is very good article at serverfault. You can find there further explanations.

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29. May 2013 at 21:58 - Software engineering (Tags: , , , ). Both comments and pings are currently closed.

One Response to “Solution: KVM guest IO very slow”

  • techguy says:

    lib-virt has crappy default for windows guest… This resolve the issue, Thanks!

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