On 12/07/2021 08:25, Ulli Horlacher wrote:

On Sat 2021-07-10 (16:17), Chris Murphy wrote:

quoted

On Sat, Jul 10, 2021 at 12:56 AM Ulli Horlacher
[off-list ref] wrote:

quoted

root@tsmsrvj:# snaprotate -v test 5 /data/fex/spool
$ btrfs subvolume snapshot -r /data/fex/spool /data/fex/spool/.snapshot/2021-07-10_0849.test
Create a readonly snapshot of '/data/fex/spool' in '/data/fex/spool/.snapshot/2021-07-10_0849.test'

I think this might be the source of the problem. Nested snapshots are
not a good idea, it causes various kinds of confusion.

I do not have nested snapshots anywhere.
/data/fex/spool is not a snapshot.

But it is the subvolume which is being snapshotted. What happens if you
put the snapshots somewhere that is not part of that subvolume? For
example, create /data/fex/snapshots, snapshot /data/fex/spool into a
snapshot in /data/fex/snapshots/spool/2021-07-10_0849.test, export
/data/fex/snapshots using NFS and mount /data/fex/snapshots on the client?

/data/fex/spool/.snapshot/2021-07-10_0849.test is a simple snapshot of
the btrfs subvolume /data/fex/spool

quoted

quoted

We cannot move the snapshots to a different directory. Our workflow
depends on snaprotate:

http://fex.belwue.de/linuxtools/snaprotate.html

Won't snaprotate follow softlinks? ln -s /data/fex/snapshots
/data/fex/spool/.snapshot

quoted

OK does the problem happen if you have no nested snapshots (no nested
subvolumes of any kind) in the NFS export path?

If the problem doesn't happen, then either the tool you've chosen needs
to be enhanced so it will create snapshots somewhere else, which Btrfs
supports, or you need to find another tool that can.

Without snapshots there is no problem, but we need access to the snapshots
on the nfs clients for backup/recovery like Netapp offers it.
But Netapp is EXPENSIVE :-}

My server snapshots data subvolumes into a different part of the tree
(in my case I use btrbk) and exports them to clients and the clients can
access all the snapshots over NFS perfectly well.