On Nov 29, 2006 09:02 -0500, Theodore Tso wrote: > On Tue, Nov 28, 2006 at 09:20:26PM -0800, Andreas Dilger wrote: > > This is a good reason for the multi-mount protection feature that I > > proposed previously. It would mark the filesystem as in-use on one > > node and the filesystem itself would refuse to mount on the second > > node. Unfortunately, this idea met resistance from some of the > > other ext3 developers from merging it upstream. > > The resistance was because it means we have to put what is effectively > a cluster filesystem's distributed lock manager (DLM) just to tell > users that "News flash! ext3 isn't a cluster filesystem" and then > error-out the mount. Granted, it was a relatively simple cluster DLM, > but that's what you effectively need, complete with issues surrounding > heartbeats for liveness detection --- and since it was a simple > cluster DLM, it didn't handle temporary connectivity failure since > there was no STONITH (shoot-the-other-node-in-the-head) functionality. > So it didn't even solve the problem completely. I agree that the proposed MMP code is by no means a 100% solution, and is not intended to replace HA + STONITH. Rather, it is intended to handle the "oops, HA is broken, admin set it up incorrectly, FC routing broke, SCSI devices were renamed, etc" kind of issues. > Still, if a lot of users are making this fundamental mistake of trying > to use ext3 as a cluster filesystem, maybe we need to revisit this > question, since hopefully once the user sees the error message they > won't keep doing this. The only reason I raised this again was because this "mount ext2/3 on two nodes, one being read-only" is a fairly common thing for users to try and it really deserves some kind of attention. The ability to have multi-host block devices is only increasing I think, especially in server-type environments with FC, IB, ISCSI, etc. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. _______________________________________________ Ext3-users mailing list Ext3-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/ext3-users
