[pve-devel] qemu 7.0 : fleecing backup (aka: local temp write cache"
Alexandre.DERUMIER at groupe-cyllene.com
Sun Jul 31 17:58:26 CEST 2022
Currently, proxmox backup are using copy-before-write to have snapshot
This works great until you have a slow or remote storage with higher
latencies than the vm storage.
This can slowdown a lot the vm is a lot of writes occur when backup is
running. (or even can hang the vm if backup storage goes down during the
qemu backup support since 1-2 years some kind of local write cache,
When backup is running, if a block is not yet backuped, it's going to a
temp local disk image.
Some improvements have been made in qemu 7.0, previously only qcow2 was
allowed for the temp disk, now it's working with any disk
Could it be possible to implement same king of cache for proxmox backup ?
I think qemu implementation is a simple block filter (It's even possible
to expose a virtual snasphot), so maybe it could be easy to implement it ?
This is really a blocker for me,I can't use pbs because I'm using nvme
is production, and a 7200k hdd backup in a remote 200km site with 5ms
If I could use temp nvme cache on the hypervisor, it could be wonderfull :)
I had opened a bugzilla some week ago with same kind of local cache idea
(didn't known about qemu fleecing at this time, seem the way to go)
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