Testing Linux multipathd SAN paths

1. Format and mount the SAN LUN.
2. Start a write to the mounted filesystem cat /dev/zero » /pathto/mnt/testfile &
3. Now connect to the multipath daemon in interactive mode multipathd -k
4. View current paths with show maps topology

multipathd> show maps topology
reload: mpath5 (360060e801045249004f2a5f900000031) dm-7 HITACHI,DF600F
[size=128G][features=0][hwhandler=0][rw]
\_ round-robin 0 [prio=1][active]
\_ 1:0:0:4 sdb 8:16 [active][ready]
\_ round-robin 0 [prio=0][enabled]
\_ 2:0:0:4 sdc 8:32 [active][ready]

5. There are two paths shown as sdb and sdc. Delete one path.

del path sdb

6. Suspend with ctrl-z and check that the write is still happening.

ls -l /pathto/mnt If testfile is still growing then the path sdc is working.

7. Resume multipath with fg 2. Re-add the path.

add path sdb

8. Now remove the other path.

del path sdc

9. Again suspend iwth ctrl-z and check that the test file is growing. If so then resume multipath and re-add the path.

add path sdc

10. Testing complete. Exit with ctrl-c. Kill the write job with kill %1. Remove the test file.