local-lvm on a new installation

[saint_antone]

What is the purpose of the local-lvm on a new installation of Proxmox VE? Can the space be reclaimed and repurposed into a directory so that it will also be able to store snapshots, backups, and others?

https://dannyda.com/2020/05/10/how-...-proxmox-ve-pve-and-some-lvm-basics-commands/

 

[fiona]

Hi,

What is the purpose of the local-lvm on a new installation of Proxmox VE?

it's intended to store disks/volumes for VMs and containers.

Can the space be reclaimed and repurposed into a directory so that it will also be able to store snapshots, backups, and others?

https://dannyda.com/2020/05/10/how-...-proxmox-ve-pve-and-some-lvm-basics-commands/

Yes, you can if you need features only a file-system based storage offers. But note that LVM-Thin also supports snapshots.

 

[saint_antone]

Hello Fabian,

Would you know where at the OS level can local-lvm be accessed? Say, I'd like to retrieve the files of the virtual machine for the snapshots, with intention of moving it to another Proxmox installation that is not part of a cluster.

 

[fiona]

With LVM you have virtual block devices, which you can list with the command lvs. For snapshots on LVM-thin, Proxmox VE creates volumes named e.g. pve/snap_vm-1039-disk-0_testsnap. To access such a volume directly, you can use lvchange -ay -K pve/snap_vm-1039-disk-0_testsnap (activates the volume) and then it should show up in /dev/mapper/.

But the much easier way to move a VM from one installation to another is to create a backup and restore it on the other node.

 

[saint_antone]

Hi Fabian,

That recommendation of using backup and restore is the best option, indeed. I tried it and it works perfectly! Thanks a lot for sharing that.

One question though, but not related to backup and restore. If I have a primary disk (NVMe, which is reasonably small in terms of capacity) and an array of disks (which is relatively bigger in terms of capacity) configured as RAID0 to store the virtual machines, is it possible to move the ZST files from the primary disk to the data disk?

I tried using lsblk to display the layout and indeed the virtual blocks are there. It is unclear to me though on how I can create my own "virtual block" so I can store the ZST files there. This way, it does not have to consume the very limited NVMe space. Since they will be there as cold backup, then probably it does not make sense for them to be in NVMe anyway.

 

[saint_antone]

Yes, you can if you need features only a file-system based storage offers. But note that LVM-Thin also supports snapshots.

Do you mind sharing the procedure for how this can be achieved? I tried looking at the web interface of proxmox, and from there, I see "no disks unused."

 

[fiona]

Do you mind sharing the procedure for how this can be achieved? I tried looking at the web interface of proxmox, and from there, I see "no disks unused."

Well in Proxmox VE, LVM-thin doesn't support storing backups. That is one of the features "only a file-system based storage offers". Sorry if I wasn't clear enough on that.

You can create a logical volume in the thin pool lvcreate -V <size>G --name <name> --thinpool <volume group>/<thin pool> with a file system on top of the logical volume, e.g. mkfs.ext4 /dev/mapper/<volume group>-<name>. Then you can mount the file system and add it as a directory storage to Proxmox VE. It's of course not the nicest solution, but might still be better than needing to re-partiton everything