space requirement for local tmp dir ?


Well-Known Member
Feb 14, 2018
I'm doing backups on an NFS Share, and I'm looking to increase the speed.
Log says « temporary directory is on NFS, (...) consider configuring a local tmpdir via /etc/vzdump.conf"

My understanding is setting up a local tmp dir means it will be faster (it won't copy over network twice).

But does it mean my tmp dir has to have enough space to hold the whole backup ? I have an LXC container with about 300G data on it, do I need to have 300G free space on my tmp dir ?
Local storage. It's a small setup, just one proxmox server with local storage, and an NFS Server to store the backups.

My understanding is that backing up first syncs the container to tmp, then archives and compresses this tmp to the final destination tar.lzo file.

So in fact I have 2 related questions :
- if I set up a local tmp, to backup a 300G container I need 300G extra space on the local storage to store the tmp sync, am I right ?
- and if I DON'T set up a local tmp, I need 2 x 300 GB = 600 GB free space on my NFS server : 300GB to store the tmp sync, and another 300GB to store the final .tar.lzo file (a little bit less in reality because of compression). Am I right too ?

I have exactly the same problem : 100GB space left on my 500GB local storage and a 180GB container that I want to backup to my NFS backup storage.

Did you found a solution ?
Well, kinda...I added some more disks !

The first phase of a backup creates an exact replica of the container in a tmp dir (no compression here).
In the second phase, it compresses the replica and sends it to its final destination (backup dir)

So yes, to backup a 300G container you need 300GB tmp space, plus 300GB backup space (a little bit less because of compression)
Hi !

Wow... in my case I'm working with a 512 GB SSD dedicated server, so I could never use a container of more than 256 GB if I want to be able to backup it... Proxmox costs us then very expensive :/
you only need a tmpdir for suspend mode, if your storage supports snapshots, or you do your backups offline, you don't need any extra space except for what the actual backup takes.
that was in suspend mode as well..
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@sebalou, note : if you choose snapshot mode (like you did) and your underlying FS doesn't support snapshots, then Proxmox falls back to suspend mode (which needs a lot of disk space)

So, in your case, I see two solutions :
- stop mode, if you can afford to take your container offline during the backup
- or install your system on a FS that supports snapshots, like ZFS, then you can do snapshot mode bakups that won't fallback to suspend


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