RAFT and CTDB

[Martin Schwenke]

On Sat, 6 Dec 2014 15:55:28 +1100, Martin Schwenke <martin at meltin.net>
wrote:

> As various people have mentioned, the default filesystem requirement
> is fcntl(2) locking support to support the CTDB recovery lock.
> There's an assumption that if the ping_pong test succeeds then CTDB's
> recovery lock will work.  If that's not true then we need to create a
> new test.  However, I don't believe anyone has conclusively shown
> ping_pong not to be a reliable test.

I rushed through some of this late on Saturday night and was actually
fooled.  I thought the ping_pong test had passed and then CTDB failed
in the same way that some people have described on this mailing list.

I have since updated the ping_pong wiki page at:

  https://wiki.samba.org/index.php/Ping_pong

by adding some bold and an extra section.

The summary is that you can't race through and simply confirm that the
test prints the correct data_increment value when running with -rw.

For the recovery lock to work you need to run the non -rw version and
actually confirm that *the locking rate drops dramatically*.  If it
doesn't then it is *not* working!

peace & happiness,
martin