backup large vm

[bumann]

hi,

i have a 4tb vm on my pve host. The storage is a nfs share on pve host via 10g network. The performace of the pve host is good.
So i want to backup the vm on a proxmox backup server with local zfs drives connected via 10g network.
The first backup takes around 6h. A Backup after a day performes in a few minutes.
But after a restart of the vm, the backups takes 6h.

 

[flames]

Are you sure it is just after restart, or is it after shutdown + start?
The fast PBS backups are based on Qemu dirty bitmap, witch tracks the changes on virtual disk, if you stop your VM the bitmap is reset, so backup needs to reread the whole disk image again. Still backup does write only needed blocks.
see here https://pbs.proxmox.com/docs/technical-overview.html?highlight=dirty
and look in your backup log, you see "created new dirty bitmap" after halt+start the vm https://forum.proxmox.com/threads/dirty-bitmap-status-created-new.75771/

 

[bumann]

ok, thanks for the info. so the problem is only when i shutdown vm

in the past i think i had problems with nfs and trim/discard with my qcow vms.
do you think i can push the 6h to for example to 3h if trim works?