[Samba] Winbind process stuck at 100% after changing use_mmap to no

[Volker Lendecke]

On Fri, Jul 01, 2016 at 10:00:21AM +0100, Alex Crow wrote:
> We've had a strange issue after following the recommendations at
> https://wiki.samba.org/index.php/Ping_pong, particularly the part
> about mmap coherence. We are running CTDB/Samba over a MooseFS
> clustered FS, and we'd not done the ping-pong before. After finding
> that the mmap coherence test did not pass, we changed "use mmap" to
> "no" in smb.conf.

"use mmap" only affects tdbs, which should not sit on the clustered
fs, they should *always* be on a local file system like ext4, assuming
you're using Linux. The wiki page above states that it's not
absolutely essential to provide mmap coherence, so you should not
bother too much.

Or are you putting tdb files on moosefs?

BTW, the straces you're seeing are probably not real spins, that's
traverses. With 10000 hash chains, that will be 10000 preads. That's
just taking time. If the tdbs sit on moosefs, it might actually be
true that it does not like that. But as I said: Never put tdbs on a
cluster file system. If cluster file systems did that access pattern
fine, ctdb would not exist :-)

Volker