Symptoms

A single disk path is available to a disk.A disk is reporting a missing disk path.Event/Alert: EVT-MPATH-00005: The number of active paths to a disk has decreased. Multipath redundancy has been lost unless there are more than one connection paths.

Cause

Missing disk/SAS path to a disk.

Resolution

The workaround is to toggle the affected SAS/Disk path, as follows: Identify the active path that the drive is on: #disk multipath status Example Output: Disk Multipath Status ---------------------------------------------------------------------------------- Port Hops Status Disk ---- ---- ------- --------------- 2a 1 Active 2.1 - 2.16 3 Standby 4.1 - 4.16 2 Active 6.1 - 6.16 4 Standby 8.1 - 8.16 2b 3 Standby 3.1 - 3.16 1 Active 5.1 - 5.16 2 Active 7.1 - 7.8 2 Standby 7.9 - 7.16 2c 0 Active 9.1 - 9.8 0 Standby 9.9 - 9.15 3a 1 Active 3.1 - 3.16 3 Standby 5.1 - 5.16 2 Active 7.9 - 7.16 2 Standby 7.1 - 7.8 3b 4 Standby 2.1, 2.3 - 2.16 <<<---- Disk 2.2 is missing a path on SAS port 3b 2 Active 4.1 - 4.16 3 Standby 6.1 - 6.16 1 Active 8.1 - 8.16 3d 0 Active 9.9 - 9.15 0 Standby 9.1 - 9.8 ----------------------------------------------------------------------------------- In ALL cases, try non-disruptive recovery by rescanning the affected disk slot: # disk rescan Example: # disk rescan 2.2 If the disk rescan does not recover the missing path, then the steps below can be followed:Determine the missing disk path and its related SAS/HBA Port numbers:Useful commands to achieve this are: # disk port show summary # disk multipath status # enclosure show topology # log watch debug/plaform/kern.info Note:A stable backend/system has little to no scrolling in kern.info;Expect plenty of output when making changes that impact the SAS chain. Example, when a disk path is disabled. Seek necessary approval and then proceed to Disable the file system, by issuing the command: #filesys disable i.) Disable the port with the missing path. Issue the command: DO NOT disable the active/remaining path (in this example: 2a) #disk port disable In the example above, path 3b would be disabled by running the command: #disk port disable 3b ii.) Wait for 2 minutes to allow paths to failover to single/remaining SAS path: After 2 minutes, check and confirm that the paths have failed over successfully, then; Proceed to re-enable the affected port: #disk port enable Allow 2 minutes for the system to remap the disk paths: For example, #disk port enable 3b Now run a topology/IO test down the affected path: # enclosure test topology duration In the example above, the syntax would be: # enclosure test topology 3b duration 2 Verify that the secondary path is now active. Run the command: # disk multipath status Re-enable the file system once pathing issue is resolved: # filesystem enable

Support Cases