QCOW2 on ZFS, but over NFS?

[mambojuice]

We all know that a COW disk on a COW filesystem is bad, but what if the underlying storage is over NFS?

I haven't been able to find a definitive answer, but I would imagine that QCOW2 disk images on NFS storage should be safe from write amplification even if the underlying NFS storage is ZFS.

Wouldn't the QCOW2 copy-on-write occur on the PVE host, while the raw storage copy-on-write happens on the ZFS box? Or am I way off in my assumption?

 

[alexskysilk]

nfs is just the transport. no special magic occurs because thats what you are using for connectivity.

 

[IsThisThingOn]

We all know that a COW disk on a COW filesystem is bad, but what if the underlying storage is over NFS?

That makes it even worse by introducing another abstraction layer.

but I would imagine that QCOW2 disk images on NFS storage should be safe from write amplification even if the underlying NFS storage is ZFS.

No. Why should that be the case?

Wouldn't the QCOW2 copy-on-write occur on the PVE host, while the raw storage copy-on-write happens on the ZFS box? Or am I way off in my assumption?

So you want to move of the storage from PVE to a ZFS box and access it over NFS?
So then the no copy on write happens on your PVE host but you still have copy on write twice, plus you added NFS, you just moved the problem to another box.