Today I tried to patched my RAC One Node (2 node) cluster to 126.96.36.199.8. I was on 188.8.131.52.6 prior to this.
I started by only patching Grid Infrastructure & DB home on node 2. The GI patch was successful but the DB patch had 1 failure so I decided to rollback the DB patch - this also rolled back my GI patch.
Everything was back to 184.108.40.206.6 and when I tried to restart my acfs resource on node 2 it failed to start with an ACFS/ADVM kernel not supported error. The acfs resource was working on node 1 which has exactly the same kernel version!!!!
After loads of searching I found out that although Oracle had rolled back the patch, it didn't update or use the correct osds_acfslib.pm (located in $GRID_HOME/lib). This file that Oracle either replaced with a vanilla copy of modified didn't have a section in it for
my kernel version - 2.6.32-400
I therefore copied the fresh copy of this file from node 1 to node 2 and then ran
acfsload start -s
lsmod | grep oracle
--- this then showed
crsctl start res <acfs resource name> -n <node name>
ACFS started fine after this! Hope it helps someone...