libvirt users - Feb 2014 - Connecting disks to controller virtio-scsi of qemu/kvm

Hello,

in another mail list with another issue I had problems with HTML 
content. Due no response I send my question in PLAIN/TEXT again.

Bye Markus


-------- Original-Nachricht --------
Betreff: 	Connecting disks to controller virtio-scsi of qemu/kvm
Datum: 	Wed, 05 Feb 2014 18:37:06 +0100
Von: 	chickenmarkus@freenet.de
An: 	libvirt-users@redhat.com



Hello,

I try to use the virtio-scsi driver to use my disks. But my setup at first:

  * in general Debian Wheezy
  * Kernel: 3.11-0.bpo.2-amd64
    (http://packages.debian.org/wheezy-backports/linux-image-3.11-0.bpo.2-amd64)
  * Qemu-KVM: 1.7.0 (http://packages.debian.org/jessie/qemu-kvm)
  * Virsh 1.2.1 (http://packages.debian.org/jessie/libvirt-bin)

The new kernel and dirty things from Jessie are for discard support 
(also not working with current configuration despite thin volumes with 
working discard). Once I have the this "new" qemu version, why not to 
use virtio...

Every disk with target bus "scsi" gets an own scsi-hd device. Libvirt 
ignores the scsi controller of type virtio-scsi.
Here is a XML snippet:

    <devices>
    <controller type='scsi' model='virtio-scsi'
index="0"/>
    <disk type="block" device="disk">
         <source dev="/dev/ssd0/sarabi"/>
         <driver discard="unmap"/>
         <target dev="sda" bus="scsi"/>
         <address type="drive" controller="0" bus=0/>
    </disk>
    </devices>

This creates the virtio-scsi controller (verified by lspci in guest) but 
do not "connect" the disks to it. The resulting command line looks 
following:

    kvm [...] -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x5 -drive
    file=/dev/ssd0/sarabi,if=none,id=drive-scsi0-0-0-0,format=raw,discard=unmap
    -device
   
scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=2
    [...]


How get my disk to run over virtio-scsi? Or did I found something like a 
bug?

Bye Markus

Hello,

after another issue with discard I understood how it works.

-device virtio-scsi-pci,id=scsi0
--> Creates the controller with id scsi0.
-drive file=/dev/ssd0/sarabi,if=none,id=drive0
--> Initialize only (if=none) an image/volume to use.
-device scsi-hd,bus=scsi0.0,drive=drive0
--> Creates the disk on base of drive0 and connect it to port 0 of 
controller scsi0 over bus=scsi0.0.

Thanks for not killing me.

Bye Markus




Am 07.02.2014 16:30, schrieb chickenmarkus@freenet.de:
> Hello,
>
> in another mail list with another issue I had problems with HTML 
> content. Due no response I send my question in PLAIN/TEXT again.
>
> Bye Markus
>
>
> -------- Original-Nachricht --------
> Betreff:     Connecting disks to controller virtio-scsi of qemu/kvm
> Datum:     Wed, 05 Feb 2014 18:37:06 +0100
> Von:     chickenmarkus@freenet.de
> An:     libvirt-users@redhat.com
>
>
>
> Hello,
>
> I try to use the virtio-scsi driver to use my disks. But my setup at 
> first:
>
>  * in general Debian Wheezy
>  * Kernel: 3.11-0.bpo.2-amd64
>
(http://packages.debian.org/wheezy-backports/linux-image-3.11-0.bpo.2-amd64)
>  * Qemu-KVM: 1.7.0 (http://packages.debian.org/jessie/qemu-kvm)
>  * Virsh 1.2.1 (http://packages.debian.org/jessie/libvirt-bin)
>
> The new kernel and dirty things from Jessie are for discard support 
> (also not working with current configuration despite thin volumes with 
> working discard). Once I have the this "new" qemu version, why
not to
> use virtio...
>
> Every disk with target bus "scsi" gets an own scsi-hd device.
Libvirt
> ignores the scsi controller of type virtio-scsi.
> Here is a XML snippet:
>
>    <devices>
>    <controller type='scsi' model='virtio-scsi'
index="0"/>
>    <disk type="block" device="disk">
>         <source dev="/dev/ssd0/sarabi"/>
>         <driver discard="unmap"/>
>         <target dev="sda" bus="scsi"/>
>         <address type="drive" controller="0"
bus=0/>
>    </disk>
>    </devices>
>
> This creates the virtio-scsi controller (verified by lspci in guest) 
> but do not "connect" the disks to it. The resulting command line
looks
> following:
>
>    kvm [...] -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x5 -drive
> file=/dev/ssd0/sarabi,if=none,id=drive-scsi0-0-0-0,format=raw,discard=unmap
>    -device
>
scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=2
>    [...]
>
>
> How get my disk to run over virtio-scsi? Or did I found something like 
> a bug?
>
> Bye Markus
>
>
>
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