vzdump - trying to improve speed

chrisalavoine

Well-Known Member
Sep 30, 2009
152
0
56
Hi all,

I have 4 Proxmox hosts running 1.6 (2.6.35) netdev from pvetest

Code:
pve-manager: 1.6-8 (pve-manager/1.6/5296)
running kernel: 2.6.35-1-pve
proxmox-ve-2.6.35: 1.6-7
pve-kernel-2.6.35-1-pve: 2.6.35-7
pve-kernel-2.6.18-2-pve: 2.6.18-5
qemu-server: 1.1-25
pve-firmware: 1.0-9
libpve-storage-perl: 1.0-16
vncterm: 0.9-2
vzctl: 3.0.24-1pve4
vzdump: 1.2-9
vzprocps: 2.0.11-1dso2
vzquota: 3.0.11-1
pve-qemu-kvm: 0.13.0-2
ksm-control-daemon: 1.0-4

I am trying to find a way to increase my vzdump snapshot times.

All my guest VM's are stored on an iSCSI SAN. Due to this all my VM's must be created as raw. I've read back through the forum and people have suggested that much better vzdump performance is achievable if you use qcow2.
Can anyone suggest any ways to increase performance without ditching my SAN storage?
I've tried creating a vzdump.conf file and have tested with various bwlimit and size setting to no avail. I seem to stuck ~10-15MiB/s backup speed. On some of my larger VM's that takes around 1.5 hours.
Presently I use compression. I think I could maybe half this time without the compression but this then has a knock-on effect as the tarballs are then backed up to an offsite location so the smaller the file the better.

Any ideas?

Cheers in advance,
Chris.
 
I can't use compression on a couple real large ones either because of the time it takes too.
Since you have a 3rd party app moving the tar offsite, maybe it can be set to compress what it's moving?

As for bwlimit tweaking it's essentially an ignored value since PVE 1.6.
Instead it uses --ionice 7 now. You can get some considerable increases by issuing --ionice 0 when you do a manual backup from the command line.

There's a file called /etc/vzdump.conf where global values are specified to be overridden.

I haven't had to try and see if adding the line
ionice: 0
would be respected, but if I had to guess that's where I'd start.

Also have a look at the vzdump manual from the wiki.
 
Thanks for that info JustaGuy.

I did look at the ionice setting but haven't tried any tests yet. I already have a vzdump.conf file so will give ionice: 0 a try on tonight's backup run.

Thanks again.
Chris.
 
the backup speed of 10-15Mib/s is bit misleading is you got your disk on block devices. the tool reads the scan the whole disk (also the empty space) before the backup process starts so this takes some time - so this speed is just an average. if you got qcow2 this is not needed.
 

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