Unique device ID for virtual hard disks?

[gurubert]

Hi,
currently virtual hard disk show up like this under /dev/disk/by-id:

lrwxrwxrwx 1 root root 9 Sep 2 13:47 scsi-0QEMU_QEMU_HARDDISK_drive-scsi0 -> ../../sda
lrwxrwxrwx 1 root root 10 Sep 2 13:47 scsi-0QEMU_QEMU_HARDDISK_drive-scsi0-part1 -> ../../sda1
lrwxrwxrwx 1 root root 10 Sep 2 13:47 scsi-0QEMU_QEMU_HARDDISK_drive-scsi0-part2 -> ../../sda2
lrwxrwxrwx 1 root root 10 Sep 2 13:47 scsi-0QEMU_QEMU_HARDDISK_drive-scsi0-part3 -> ../../sda3
lrwxrwxrwx 1 root root 10 Sep 2 13:47 scsi-0QEMU_QEMU_HARDDISK_drive-scsi0-part4 -> ../../sda4
lrwxrwxrwx 1 root root 9 Sep 2 16:56 scsi-0QEMU_QEMU_HARDDISK_drive-scsi1 -> ../../sdb
lrwxrwxrwx 1 root root 9 Sep 2 16:56 scsi-0QEMU_QEMU_HARDDISK_drive-scsi2 -> ../../sdc
lrwxrwxrwx 1 root root 9 Sep 2 17:28 scsi-0QEMU_QEMU_HARDDISK_drive-scsi3 -> ../../sdd
lrwxrwxrwx 1 root root 9 Sep 2 17:28 scsi-0QEMU_QEMU_HARDDISK_drive-scsi4 -> ../../sde
lrwxrwxrwx 1 root root 9 Sep 2 17:28 scsi-0QEMU_QEMU_HARDDISK_drive-scsi5 -> ../../sdf

They have a unique ID inside the VM.

But when looking at multiple VMs the IDs are not unique any more. A management system that spans more than one VM gets confused with multiple HDDs having the same ID.

Is it possible to replace QEMU_HARDDISK with a unique id (possibly a UUID)? Is that even something Proxmox can do?

Physical disks in physical machines do not have this issue.

 

[Stoiko Ivanov]

Is it possible to replace QEMU_HARDDISK with a unique id (possibly a UUID)? Is that even something Proxmox can do?

What you can do is add both a 'serial' and/or 'wwn' parmeter to the drive specification - e.g.:

scsi0: local:vm-100-disk-0,size=8G,serial=myserialnumber11444,wwn=0x5566777788888888

in a debian VM this results in a few links being created in /dev/disk/by-id:

/dev/disk/by-id/scsi-35566777788888888
/dev/disk/by-id/wwn-5566777788888888

out of the box - the links with the serial number don't get created - but this is something that possibly can be achieved by appropriate udev-rules inside the guest

I hope this helps!

Out of curiosity - why would you need unique identifiers for virtualized disks?

 

[gurubert]

Thanks, will try that.

I am testing Ceph on VMs, and the Dashboard gets mightily confused by the same IDs.

 

[gurubert]

Now using serial= for the task. That works.
Would be nice if that parameter could be set via GUI and API.

 

[Stoiko Ivanov]

Would be nice if that parameter could be set via GUI and API.

The use-case is something that is requested rather seldomly (my guess about once per year) - and given that the Disk-Edit GUI window is already quite heavy in terms of possible configurable options we would rather leave the more specific use cases to command-line only instead of putting even more widgets on that window

 

[gurubert]

The use-case is something that is requested rather seldomly

I understand that this would not be in the GUI. But could it be added to the API at least so that we can automatically set serials for vHDDs? Thanks.

 

[gurubert]

You could also create a random serial number (UUID ?) for each virtual disk.

 

[illustris]

GCP has this functionality. I found this thread trying to find a way to do the same thing in proxmox.

The use-case is something that is requested rather seldomly (my guess about once per year)

2022 is almost over, so here's the obligatory annual request for this feature...

Out of curiosity - why would you need unique identifiers for virtualized disks?

For example, if you want your VMs to automatically mount a disk in, say, /var/log and another in /var/lib/elasticsearch, you could set "serial=logs" and "serial=es" on those disk, and add /dev/disk/by-id/scsi-logs and /dev/disk/by-id/scsi-es to fstab. This is much better than the alternative of remembering the order of disks attached tot he VM, and referring to them as sda/b/c.
You could even have a startup script baked into VM templates to auto-format the disks on first boot.
Modifying the conf files works, but being able to do this from the UI or through the API would make more powerful templating possible.

 

[Dzung]

hi everyone, has anyone had success with this setting?, i added but when i check UniqueIdFormat does not change, i am testing to create shared disk for windows cluster
this is the error i am getting: https://www.weithenn.org/2015/09/s2d-failed-to-get-scsi-page-83h-vpd.html