Enhancing vzdump

[f4242]

Hello,

I found that my VM dumps are bigger than the used disk space inside my VMs. I made some searches and found this is because removed files from the disk are just flagged to be deleted but not removed from the disk. I understand that.

I found that I can zero-fill my free space with dd, but I think this is an ugly hack that can cause problems on production servers (this make a lot of IO for nothing and the disk become full for some time, so some process may fail to write real data on the filesystem).

Do you plan to enhance vzdump and backup only useful data blocks (ignoring data blocks marked as removed). I suspect this would need support for specific filesystems.

This would be really useful, because this make a very big waste of disk space on my backups volume.

Thanks!

 

[dietmar]

I guess you can simply run fstrim inside the VM.

 

[f4242]

I didn't tried in a node with SSD drives, but doesn't work with HDD/SAS drives.

 

[redmop]

That's what I do. On OSes that don't support it, I do a "dd if=/dev/zero of=zero.img bs=1m ; rm -v zero.img" to zero the space to the same effect though it.

 

[robhost]

I didn't tried in a node with SSD drives, but doesn't work with HDD/SAS drives.

Works also with SATA, if you use QCOW2 or LVM. You have to enable "discard" in the VM config and use virtio scsi as controller for VM.
See also https://pve.proxmox.com/wiki/Qemu_trim/discard_and_virtio_scsi

 

[mir]

Works also with SATA, if you use QCOW2 or LVM. You have to enable "discard" in the VM config and use virtio scsi as controller for VM.
See also https://pve.proxmox.com/wiki/Qemu_trim/discard_and_virtio_scsi

You will either use fstrim manually or enable discard and have it done automatically for a performance penalty.

 

[f4242]

Interesting. First try to convert an existing VM failed. VM doesn't boot (ubuntu 16.04). Reverted changes for now.

 

[robhost]

Interesting. First try to convert an existing VM failed. VM doesn't boot (ubuntu 16.04). Reverted changes for now.

Maybe you have to change /etc/fstab and GRUB Config, because virtoi uses "/dev/vda" and virto-scsi "/dev/sda".

 

[f4242]

Maybe you have to change /etc/fstab and GRUB Config, because virtoi uses "/dev/vda" and virto-scsi "/dev/sda".

Hello,

/etc/fstab use uuid instead of physical device, so I didn't changed anything in this file.

I didn't find references to /dev/vda in grub config either. I see "(hd0)", is it still good with virtio-scsi?

 

[robhost]

I didn't find references to /dev/vda in grub config either. I see "(hd0)", is it still good with virtio-scsi?

Yes, should work. You can try "grub-mkdevicemap" to make sure.

 

[f4242]

I feel a little dump... I didn't changed the boot order in the VM's options. I had to switch virtio0 disk to scsi0... Seem to do the job. Thanks!

 

[f4242]

Succeeded to switch to virtio-scsi all my Linux VMs.

I have one Windows 10 VM and this is the only VM I didn't succeeded to switch. Windows doesn't boot anymore. I booted from the install media, loaded the virtio-scsi driver and tried to "repair" the installation, Windows tries to repair itself but fail to. Reverted back to virtio and it boots again.