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.