[Qemu-devel] virtio_blk unique device ID

[Qemu-devel] virtio_blk unique device ID

[Jule Slootbeek]

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All,
I was recently testing the workings of virtio to provision SAN block devices
to a domain, which worked great! However, i could not find a way to find the
UID of a virto_blk device. The scenario I had created was the following. a
LUN provisioned to my KVM (kvm-83) hypervisor over two paths, both paths
mapped to my domain using virtio_blk. When configuring multipath-tools in
the domain I could not find a way to find the UID of the LUN in order to
create the multipath config. On a SCSI device, I would use the
/lib/udev/scsi_id tools to discover this ID. I am using libvir/qemu 0.5.1 in
Ubuntu Jaunty Alpha-3 as hypervisor and virtual machine.
Does the virtio_blk driver provide a UID to its devices, and is there a way
to get this ID in userspace?

kind regards,

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Re: [Qemu-devel] virtio_blk unique device ID

[Ryan Harper]

* Jule Slootbeek <jsslists@gmail.com> [2009-01-29 16:13]:
> All,
> I was recently testing the workings of virtio to provision SAN block devices
> to a domain, which worked great! However, i could not find a way to find the
> UID of a virto_blk device. The scenario I had created was the following. a
> LUN provisioned to my KVM (kvm-83) hypervisor over two paths, both paths
> mapped to my domain using virtio_blk. When configuring multipath-tools in
> the domain I could not find a way to find the UID of the LUN in order to
> create the multipath config. On a SCSI device, I would use the
> /lib/udev/scsi_id tools to discover this ID. I am using libvir/qemu 0.5.1 in
> Ubuntu Jaunty Alpha-3 as hypervisor and virtual machine.
> Does the virtio_blk driver provide a UID to its devices, and is there a way
> to get this ID in userspace?

use uuid?  Some distros (Ubuntu for example) mount via UUID

% blkid 
/dev/vda1: UUID="6331275f-f10d-4684-8aa8-e8aca1582b9d" TYPE="swap" 
/dev/vda2: UUID="cf121062-fd27-4151-8a68-6cb940e449fe" TYPE="ext3" 

# ls -al /dev/disk/by-uuid/
total 0
lrwxrwxrwx 1 root root 10 Jan 29 17:10 6331275f-f10d-4684-8aa8-e8aca1582b9d -> ../../vda1
lrwxrwxrwx 1 root root 10 Jan 29 17:10 cf121062-fd27-4151-8a68-6cb940e449fe -> ../../vda2

-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh@us.ibm.com

Re: [Qemu-devel] virtio_blk unique device ID

[Jule Slootbeek]

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correct, however that would assume there is a file system on that block
device
the device ID should be able to be used without the existance of a FS.

ubuntu@kvm:~$ sudo /lib/udev/scsi_id -g -u --page=0x83 /dev/sdf
360060480000190300570533030313044
ubuntu@kvm:~$ blkid /dev/sdf1
/dev/sdf1: UUID="e149b893-2970-46d8-9ee4-322d6a589828" SEC_TYPE="ext2"
TYPE="ext3"


On Thu, Jan 29, 2009 at 5:47 PM, Ryan Harper <ryanh@us.ibm.com> wrote:

> * Jule Slootbeek <jsslists@gmail.com> [2009-01-29 16:13]:
> > All,
> > I was recently testing the workings of virtio to provision SAN block
> devices
> > to a domain, which worked great! However, i could not find a way to find
> the
> > UID of a virto_blk device. The scenario I had created was the following.
> a
> > LUN provisioned to my KVM (kvm-83) hypervisor over two paths, both paths
> > mapped to my domain using virtio_blk. When configuring multipath-tools in
> > the domain I could not find a way to find the UID of the LUN in order to
> > create the multipath config. On a SCSI device, I would use the
> > /lib/udev/scsi_id tools to discover this ID. I am using libvir/qemu 0.5.1
> in
> > Ubuntu Jaunty Alpha-3 as hypervisor and virtual machine.
> > Does the virtio_blk driver provide a UID to its devices, and is there a
> way
> > to get this ID in userspace?
>
> use uuid?  Some distros (Ubuntu for example) mount via UUID
>
> % blkid
> /dev/vda1: UUID="6331275f-f10d-4684-8aa8-e8aca1582b9d" TYPE="swap"
> /dev/vda2: UUID="cf121062-fd27-4151-8a68-6cb940e449fe" TYPE="ext3"
>
> # ls -al /dev/disk/by-uuid/
> total 0
> lrwxrwxrwx 1 root root 10 Jan 29 17:10 6331275f-f10d-4684-8aa8-e8aca1582b9d
> -> ../../vda1
> lrwxrwxrwx 1 root root 10 Jan 29 17:10 cf121062-fd27-4151-8a68-6cb940e449fe
> -> ../../vda2
>
> --
> Ryan Harper
> Software Engineer; Linux Technology Center
> IBM Corp., Austin, Tx
> ryanh@us.ibm.com
>

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