Hmm, here is an example. Re: [Ocfs2-users] Also just a comment to the Oracle guys

[Luis Freitas]

Alexei,
   
      Actually your log seems to show that CSSD (Oracle CRS) rebooted the node before OCFS2 got a chance to do it.
   
      On a RAC cluster, if the interconnect is interrupted, all the nodes hang until a split brain resolution is complete and the recovery of all the crashed nodes is completed. This is needed because every read on a Oracle datablock needs a ping to the other nodes. 
   
      The view of the data must be consistent, when one node read a particular data block, the Oracle Database first ping the other nodes to ensure that they did not modify the block and still have not flushed it to disk. Another node may even forward a reply with the block, preventing the disk access (Cache Fusion). 
   
      When a split brain occurs, there is the loss of these blocks not flushed to disk, and they are rebuilt using the redo threads of the particular nodes that crashed. During this interval all the database instances "freeze", since before the node recovery is complete there is no way to guarantee that a block read from disk has not been altered on the crashed node.
   
      So the fencing is needed even if there is no disk activity, as the entire cluster becomes "hang" the moment the interconnect is down. And the timeout for the fencing must be as small as possible to prevent a long cluster reconfiguration delay. Of course the timeout must be tuned so as to be larger than ethernet switch failovers, or storage controller or disk multipath failovers. Or if possible the failover times should be reduced.
   
     Now, on the other hand, I am too having problems with OCFS2. It seems much less robust than ASM and the previous version, OCFS, specially under heavy disk activity. But I do expect these problems to get solved in the near future, as did the 2.4 kernel VM problems.
   
  Regards,
  Luis
  
Alexei_Roudnev <Alexei_Roudnev at exigengroup.com> wrote:
          Additional info - node had not ANY active OCFSv2 operations (OCFSv2 used for backups only and from another node only). So, if system just SUSPEND all FS operations and try to rejoin to the cluster, it all could work (moreover, connection to the disk system was intact, so it could close file sytem gracefully).
   
  It reveals 3 problems at once:
  - single heartbeat link (instead of multiple links)
  - timeout too short (ethernet can't guarantee 10 seconds, it can guarantee 1 minute minimum);
  - fencing even if system is passive and can remount / reconnect instead of rebooting.
   
  All we did in the lab was _disconnect 1 of trunks between switches for a few seconds, then insert it back into the socket_. No one other application failed
  (including heartbeat clusters). Database cluster was not doing anything on OCFS in time of failure (even backups).
   
  I will try heartbeat between loopback interfaces (and OCFS protocol) next time (I am just curios if it can provide 10 seconds for network reconfiguration).
   
  ...
  Feb  1 12:19:13 testrac12 kernel: o2net: connection to node testrac11 (num 0) at 10.254.32.111:7777 has been idle for 10 seconds, shutting it down. 
Feb  1 12:19:13 testrac12 kernel: (13,3):o2net_idle_timer:1310 here are some times that might help debug the situation: (tmr 1170361135.521061 now 1170361145.520476 dr 1170361141.852795 adv 1170361135.521063:1170361135.521064 func (c4378452:505) 1170361067.762941:1170361067.762967) 
Feb  1 12:19:13 testrac12 kernel: o2net: no longer connected to node testrac11 (num 0) at 10.254.32.111:7777 
Feb  1 12:19:13 testrac12 kernel: (1855,3):dlm_send_remote_convert_request:398 ERROR: status = -107 
Feb  1 12:19:13 testrac12 kernel: (1855,3):dlm_wait_for_node_death:371 5AECFF0BBCF74F069A3B8FF79F09FB5A: waiting 5000ms for notification of death of node 0 
Feb  1 12:19:13 testrac12 kernel: (1855,1):dlm_send_remote_convert_request:398 ERROR: status = -107 
Feb  1 12:19:13 testrac12 kernel: (1855,1):dlm_wait_for_node_death:371 5AECFF0BBCF74F069A3B8FF79F09FB5A: waiting 5000ms for notification of death of node 0 
Feb  1 12:22:22 testrac12 kernel: (1855,2):dlm_send_remote_convert_request:398 ERROR: status = -107 
Feb  1 12:22:22 testrac12 kernel: (1855,2):dlm_wait_for_node_death:371 5AECFF0BBCF74F069A3B8FF79F09FB5A: waiting 5000ms for notification of death of node 0 
Feb  1 12:22:27 testrac12 kernel: (13,3):o2quo_make_decision:144 ERROR: fencing this node because it is connected to a half-quorum of 1 out of 2 nodes which doesn't include the lowest active node 0 
Feb  1 12:22:27 testrac12 kernel: (13,3):o2hb_stop_all_regions:1889 ERROR: stopping heartbeat on all active regions. 
Feb  1 12:22:27 testrac12 kernel: Kernel panic: ocfs2 is very sorry to be fencing this system by panicing 
Feb  1 12:22:27 testrac12 kernel: 
Feb  1 12:22:28 testrac12 su: pam_unix2: session finished for user oracle, service su 
Feb  1 12:22:29 testrac12 logger: Oracle CSSD failure.  Rebooting for cluster integrity. 
Feb  1 12:22:32 testrac12 su: pam_unix2: session finished for user oracle, service su 
...
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