Gluster users - Oct 2008 - Posix locks AFR and high availability

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 ...

&:-)

Andrew,
Yes it should work safely. posix-locks can beloaded just above storage/posix.
Let us know if it does not work the correct way.
Krishna

On Mon, Oct 20, 2008 at 3:30 PM, Andrew McGill <list2008 at lunch.za.net>
wrote:
> 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 ...
>
> &:-)
>
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