[Linux-cluster] Cluster maintenance mode ?

[Robert Peterson]

Mark Hlawatschek wrote:
> On Tuesday 27 March 2007 18:01:04 you wrote:
>> On Tue, Mar 27, 2007 at 05:48:25PM +0200, Mark Hlawatschek wrote:
>>> Is there a way to put the cman into a kind of maintenance mode, where
>>> only one node is up and no other node is allowed to join ?  If not, are
>>> there plans to implement something like that ?
>>>
>>> The question is adressing the following issue: I'd like to enable
>>> automatic GFS filesystem checks. (localfs like every Nth mount or after
>>> M days... ) This FS check would only be allowed if no other node has the
>>> filesystem mounted or no other node is in the cluster. How can this be
>>> assured in a general way ?
> 
> Is there a possibility to do an online passive gfs_fsck, without making 
> changes to the filesystem ?
> 
> Thanks,
> 
> Mark

Hi Mark,

Until recently, I would have said yes: just do gfs_fsck -n and the -n
would answer all the questions "no" making it passive.  However, I recently
discovered that gfs_fsck apparently can silently "fix" a few minor things 
under the covers without even asking the user for permission to changes 
things.  Of course,  if the file system is mounted by any node, the gfs 
kernel module won't know about the changes, which is a problem: it's likely 
to produce "consistency" problems.

It would be a good exercise to go through the code and figure out all the
places where it can do this and make some hard decisions about this.
Right now it's not a high priority, but maybe someday I'll find the time 
to do it.

Regards,

Bob Peterson
Red Hat Cluster Suite