Thin Provisioning

[necromonger]

Hello forum users,

do I especially need hardware (SSD) for thin provisioning or is the software controlled on the side?

Kind regards

 

[H4R0]

Its software sided, but not all storage types support it.

Checkout https://pve.proxmox.com/wiki/Storage

Every storage with "snapshot" support, also supports thin-provision.

So for a default install with zfs or lvm its supported.

 

[necromonger]

Hello,

Thank you for your prompt reply. I also have a folder "Data" under LVM-thin and I can take snapshots of the VM. It also seems to be heard. Debian 10 is running in the two VMs. Do I run the fstrim.timer for the weekly marking of the no longer solving blocks?

Best regards

 

[H4R0]

Either run fstrim periodic or enable discard within the vm.

I prefer discard, enable it with (for debian 10 only):
sed -i "s/errors=remount-ro/errors=remount-ro,discard/g" /etc/fstab

And then do a reboot of the vm

Afterwards space should be freed instantly. Test it by creating a random file and remove it, monitor storage space on the hypervisor.

You also have to check "discard" and "ssd emulation" in the vm disk settings for TRIM to work.

 

[necromonger]

Hello,

Thanks for the brief introduction. Thank you very much for that. I have a short question. Discard is not entered in fstab on the host, of course I have to do that there too, right?

/etc/fstab
----------------------------------------------------
# <file system> <mount point> <type> <options> <dump> <pass>
/dev/pve/root / ext4 errors=remount-ro 0 1
UUID=CD13-962D /boot/efi vfat defaults 0 1
/dev/pve/swap none swap sw 0 0
proc /proc proc defaults 0 0
----------------------------------------------------

Do I actually have to activate fstrim as a systemd service?

Please excuse the many questions.

 

[H4R0]

Its not needed on the hypervisor for thin-provisioning.

You could enable it to get better performance out of your SSD's once they fill up. But do not enable it for HDD or SSD's that have no Trim support, otherwise data loss can occur. You can check support using "lsblk --discard" if "Disc-Gran" is not 0, trim is supported.

If you use discard within the vm, a fstrim service is not needed, its either one of them.