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SnapMirror communication failure

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If the SnapMirror active sync replication link, write IO cannot be completed because it would be impossible for a cluster to replicate changes to the opposite site.

Site A

The result on site A of a replication link failure will be an approximately 15 second pause in write IO processing as ONTAP attempts to replicate writes before it determines that the replication link is genuinely inoperable. After the 15 seconds elapses, the ONTAP cluster on site A resumes read and write IO processing. The SAN paths will not change, and the LUNs will remain online.

Site B

Since site B is not the SnapMirror active sync preferred site, its LUN paths will become unavailable after about 15 seconds.

The replication link was cut at the timestamp 15:19:44. The first warning from Oracle RAC arrives 100 seconds later as the 200 second timeout (controlled by the Oracle RAC parameter disktimeout) approaches.

2024-09-10 15:21:24.702 [ONMD(2792)]CRS-1615: No I/O has completed after 50% of the maximum interval. If this persists, voting file /dev/mapper/grid2 will be considered not functional in 99340 milliseconds.
2024-09-10 15:22:14.706 [ONMD(2792)]CRS-1614: No I/O has completed after 75% of the maximum interval. If this persists, voting file /dev/mapper/grid2 will be considered not functional in 49330 milliseconds.
2024-09-10 15:22:44.708 [ONMD(2792)]CRS-1613: No I/O has completed after 90% of the maximum interval. If this persists, voting file /dev/mapper/grid2 will be considered not functional in 19330 milliseconds.
2024-09-10 15:23:04.710 [ONMD(2792)]CRS-1604: CSSD voting file is offline: /dev/mapper/grid2; details at (:CSSNM00058:) in /gridbase/diag/crs/jfs13/crs/trace/onmd.trc.
2024-09-10 15:23:04.710 [ONMD(2792)]CRS-1606: The number of voting files available, 0, is less than the minimum number of voting files required, 1, resulting in CSSD termination to ensure data integrity; details at (:CSSNM00018:) in /gridbase/diag/crs/jfs13/crs/trace/onmd.trc
2024-09-10 15:23:04.716 [ONMD(2792)]CRS-1699: The CSS daemon is terminating due to a fatal error from thread: clssnmvDiskPingMonitorThread; Details at (:CSSSC00012:) in /gridbase/diag/crs/jfs13/crs/trace/onmd.trc
2024-09-10 15:23:04.731 [OCSSD(2794)]CRS-1652: Starting clean up of CRSD resources.

Once the 200 second voting disk timeout has been reached, this Oracle RAC node will evict itself from the cluster and reboot.