[Gluster-users] Posix locks AFR and high availability

[Andrew McGill]

Is it possible to get posix locks in a high availability configuration 
with glusterfs?  

Specifically, is it sufficient to have locking enabled on the server side 
below the AFR layer?


|glusterfsd....| |.......glusterfs client..


[u1]---[u1-lock]---+
                   :=:--afr0--+
[u3]---[u3-lock]---+          |
                              +----client/unify-----
[u2]---[u2-lock]---+          |  |
                   :=:--afr0--+  |
[u4]---[u4-lock]---+             |
                                 |  
[u5-ns]--------------------------+

Here is part of the server configuration ...

volume u1
  type storage/posix
  option directory /glusterfs/u1/export
end-volume

volume u2
  type storage/posix
  option directory /glusterfs/u2/export
end-volume

volume u1-lock
  type features/posix-locks
  subvolumes u1
end-volume

volume u2-lock
  type features/posix-locks
  subvolumes u2
end-volume

I have a bad feeling that in a race condition, half of the clients will check 
the locks on one brick while the other half will check the other brick ... 
and that simultaneous transactions may be quite happy with getting one out of 
two flocks, or only release one of the two when they are done ...

&:-)