Is Kvm vps snapshot on ZFS consistent ?

yena

Member
Nov 18, 2011
295
2
18
Hello,
is Kvm (qemu) vps ZFS snapshot consistent without qemu agent installed on guest ?

There are differences between a snapshot of an LXC vps and a KVM vps using zfs ?

Thanks!
 

wolfgang

Proxmox Staff Member
Staff member
Oct 1, 2014
4,763
316
83
Hi,
is Kvm (qemu) vps ZFS snapshot consistent without qemu agent installed on guest ?
The image itself is consistency through ZFS.
But the data in the page cache of the VM are not written.
So if you want to ensure all data are written in a snapshot you have to flush your caches.
This is done by qemu-guest-agent
 

LnxBil

Well-Known Member
Feb 21, 2015
4,094
388
83
Germany
So if you want to ensure all data are written in a snapshot you have to flush your caches.
And in addition you should use software that has integrated support for this, e.g. on Windows with every software that hooks into VSS. For others, you can use qemu-agent hooks to get e.g. a database log switch and flush to disk. But in the end, you will have only crash consistency for almost all software packages that do not have such a feature.
 

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