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Re: [vfio-users] setting up virtual disks



Here are relevant parts of my VM definition:

    <controller type='scsi' index='0' model='virtio-scsi'>
      <driver queues='4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04'
      function='0x0'/>
    </controller>

    <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='writeback' io='threads'/>
      <source dev='/dev/zvol/zdata/vdis/lublin'/>
      <target dev='sda' bus='scsi'/>
      <boot order='1'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='directsync' io='native'/>
      <source
      dev='/dev/disk/by-partuuid/c5a05f68-9f2c-4ad6-96c5-a5fc85d73d7c'/>
      <target dev='sdb' bus='scsi'/>
      <address type='drive' controller='0' bus='0' target='1' unit='0'/>
    </disk>
      <driver name='qemu' type='raw' cache='writeback' io='threads'/>
      <source dev='/dev/zvol/zdata/steam2'/>
      <target dev='sdc' bus='scsi'/>
      <address type='drive' controller='0' bus='0' target='2' unit='0'/>
    </disk>

As you can see, I've setup the controller with 4 queues and 3 devices,
of which 2 are ZFS ZVOL and 1 is raw block device. I also have plenty of
spare CPUs (2 sockets, 16 cores, 32 threads), so I'm expecting that
having 4 queues will aid IO performance.


B.


-- 
  Bronek Kozicki
  brok spamcop net

On Tue, 28 Mar 2017, at 01:21 PM, Patrick O'Callaghan wrote:
> On Tue, 2017-03-28 at 11:47 +0200, Laszlo Ersek wrote:
> > I recommend the following setup:
> > 
> > - hard disk(s):          virtio-blk or virtio-scsi disk, as you prefer
> 
> I'm interested in why someone would prefer one over the other. Can you
> explain?
> 
> poc
> 
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