Red Hat Bugzilla – Bug 170926
gfs does not respect loss of quorum (split brain?)
Last modified: 2010-01-11 22:08:11 EST
Description of problem: When a cluster looses quorum, cluster members can still read/write from/to a gfs mount. Version-Release number of selected component (if applicable): kernel-smp-2.6.9-22.EL GFS-kernel-smp-2.6.9-42.1 cman-kernel-smp-2.6.9-39.5 GFS-6.1.2-0 cman-1.0.2-0 How reproducible: always Steps to Reproduce: 1.create a three node cluster and use a shared gfs mount. 2.shutdown the cluster services on two nodes 3.continue using the gfs mount on the third node Actual results: Read/write operations are possible even though the cluster has lost quorum. Expected results: gfs should respect cman's "quorum lost, blocking activity" (or cman should freeze the gfs mount until quorum is regained). Additional info: This bug possibly explains the split brain behaviour of bug #169693.
This is the correct behavior as explained in bz 162725. If a cluster loses quorum but none of the nodes mounting gfs fs "foo" have failed, then there's no need to block locking for foo (that's only needed to safely do journal recovery.) While the cluster is inquorate, no nodes are permitted to mount or unmount any gfs file systems, though. If there's a cluster partition, nodes on the inquorate side will be fenced by the quorate side before any nodes on the quorate side can mount any gfs file systems. So, if there are nodes using "foo" in an inquorate cluster, and a cluster partition gains quorum, those nodes using foo will be fenced before any nodes in the quorate cluster mount foo. *** This bug has been marked as a duplicate of 162725 ***