[Linux-cluster] GFS locks recovery

[Christos Triantafillou]

Hello,

I am using a RHEL4 cluster with 2 nodes, GFS and fencing.

As a test, I started a process on node2 that got an fcntl() exclusive lock 
on a GFS file
and then a process on node1 that started the same program waiting for an 
exclusive
lock on the same GFS file.
Node2 was then switched off and rebooted.

What I observed was that node1 did not acquire the lock immediately after 
the switch-off  but only when node2 finished rebooting.

A few questions:
1. when a node goes down, shouldn't all its GFS locks be (almost) 
immediately released as part of the fencing proces or the GFS recovery on 
the other nodes?

2. during the lock wait, it was impossible to interrupt/kill the process on 
node1.
Is it possible to interrupt a process waiting on a POSIX lock?

3. if the previous are not possible, would it be preferable to use POSIX 
locks on an NFS file instead?
Or would you recommend using DLM?

Thanks in advance for your answers,
Christos Triantafillou

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