On Fri, Jan 28, 2022 at 08:38:43AM -0500, J. Bruce Fields wrote: > On Fri, Jan 28, 2022 at 03:14:51PM +1100, NeilBrown wrote: > > On Fri, 28 Jan 2022, J. Bruce Fields wrote: > > > I don't see how it's going to work. You've got clients that hold locks > > > an opens on the unexported filesystem. So maybe you can use an NFSv4 > > > referral to point them to the new server. Are they going to try to > > > issue reclaims to the new server? There's more to do before this works. > > > > As I hope I implied, I'm not at all sure that the specific problem that > > the customer raised (cannot unmount a filesystem) directly related to > > the general solution that the customer is trying to create. Some > > customers like us to hold their hand the whole way, others like to (feel > > that they) have more control. In general I like to encourage > > independence (but I have to consciously avoid trusting the results). > > > > We have an "unlock_filesystem" interface. I want it to work for NFSv4. > > The HA config was background, not a complete motivation. > > I think people do occasionally need to just rip a filesystem out even if > it means IO errors to applications. And we already do this for NFSv3. > So, I'm inclined to support the idea. > > (I also wonder whether some of the code could be a useful step towards > other functionality.) For example, AFS-like read-only replica update: unmount a filesystem, mount a new version in its place. "Reconnecting" locks after the open would be difficult, I think, but opens should be doable? And in the read-only case nobody should care about locks. --b. > > > > > However I don't think we have good admin infrastructure for that do > > > > we? > > > > > > > > I'd like to be able to say "set up these 2 or 3 config files and run > > > > systemctl start nfs-server@foo and the 'foo' network namespace will be > > > > created, configured, and have an nfs server running". Do we have > > > > anything approaching that? Even a HOWTO ?? > > > > > > But I don't think we've got anything that simple yet? > > > > I guess I have some work to do.... > > RHEL HA does support NFS failover using containers. I think it's a bit > more complicated than you're looking for. Let me go dig that up.... > > With a KVM VM and shared backend storage I think it's pretty easy: just > shut down the VM on one machine and bring it up on another. > > --b.
