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Re: [dm-devel] failed multipaths are never re-validated



Guy Coates wrote:

Hi,

I have a dual fabric / dual contoller setup which I've got partially to
work with the multipath device mapper personality. I can create a
multipath device and I can get multipathd to remove failed paths to the
storage.  However, once failed paths become active again, multipathd never
adds the paths back into the devicemap.



The multipath tools correctly identify the four paths to the storage and
created the appropraite map.


ia64g:~# multipath -v -d # all paths : 600508b40001045d0001c00006de0000 (2 0 0 1) /dev/sdc [HSV110 (C)COMPAQ] 600508b40001045d0001c00006de0000 (2 0 1 1) /dev/sdd [HSV110 (C)COMPAQ] 600508b40001045d0001c00006de0000 (3 0 0 1) /dev/sde [HSV110 (C)COMPAQ] 600508b40001045d0001c00006de0000 (3 0 1 1) /dev/sdf [HSV110 (C)COMPAQ] # all multipaths : 600508b40001045d0001c00006de0000 \_(2 0 0 1) /dev/sdc [HSV110 (C)COMPAQ] \_(2 0 1 1) /dev/sdd [HSV110 (C)COMPAQ] \_(3 0 0 1) /dev/sde [HSV110 (C)COMPAQ] \_(3 0 1 1) /dev/sdf [HSV110 (C)COMPAQ]

ia64g:~# multipath
U:600508b40001045d0001c00006de0000:0 209715200 multipath 2 round-robin 2 0
/dev/sdc /dev/sde round-robin 2 0 /dev/sdd /dev/sdf

ia64g:~# dmsetup  status
600508b40001045d0001c00006de0000: 0 209715200 multipath 2 2 0 8:32 A 1 8:64 A 1 2 0 8:48 A 1 8:80 A 1


I can format the multipath device and IO does indeed go down both SAN fabrics.

If I pull one of the fabrics, multipathd correctly reconfigures the
device, and IO continues down a single fabric.

<syslog>
May 28 15:16:46 ia64g kernel: qla2300 0000:40:01.1: LOOP DOWN detected.
May 28 15:16:54 ia64g kernel: SCSI error : <3 0 0 1> return code = 0x10000
May 28 15:16:54 ia64g kernel: end_request: I/O error, dev sde, sector 33967656

May 28 15:15:33 ia64g /usr/bin/multipathd: [event thread] refresh failpaths list
May 28 15:15:33 ia64g /usr/bin/multipathd: [event thread] start up event loops
May 28 15:16:59 ia64g /usr/bin/multipathd: [checker thread] reconfigure 600508b40001045d0001c00006de


ia64g:~# dmsetup status 600508b40001045d0001c00006de0000: 0 209715200 multipath 2 2 0 8:32 A 1 8:64 F 0 2 0 8:48 A 1 8:80 A 1

ia64g:~# multipath -d -v
# all paths :
600508b40001045d0001c00006de0000 (2 0 0 1) /dev/sdc [HSV110 (C)COMPAQ]
600508b40001045d0001c00006de0000 (2 0 1 1) /dev/sdd [HSV110 (C)COMPAQ]
00000000000000000000000000000000 (3 0 0 1) /dev/sde [HSV110 (C)COMPAQ]
00000000000000000000000000000000 (3 0 1 1) /dev/sdf [HSV110 (C)COMPAQ]
# all multipaths :
600508b40001045d0001c00006de0000
 \_(2 0 0 1) /dev/sdc [HSV110 (C)COMPAQ]
 \_(2 0 1 1) /dev/sdd [HSV110 (C)COMPAQ]
00000000000000000000000000000000
 \_(3 0 0 1) /dev/sde [HSV110 (C)COMPAQ]
 \_(3 0 1 1) /dev/sdf [HSV110 (C)COMPAQ]


When I reconnect the seconds fabric, the newly active path does not get automatically added back into the device map.

May 28 15:19:02 ia64g kernel: qla2300 0000:40:01.1: LIP reset occured (f7f7).
May 28 15:19:02 ia64g kernel: qla2300 0000:40:01.1: LOOP UP detected (2 Gbps).

ia64g:~# dmsetup  status
600508b40001045d0001c00006de0000: 0 209715200 multipath 2 2 0 8:32 A 1 8:64 F 0 2 0 8:48 A 1 8:80 A 1

At this point, has multipathd retested the paths, or are you hoping that the loop up event will trigger the multipathd? I do not think the latter is possible today (see below), but once the multipathd tests the paths they should readded to the multipath device. Does the retesting part not work too?



I can force a reconfiguration manually by issuing the "multipath" command again.

ia64g:~# multipath
U:600508b40001045d0001c00006de0000:0 209715200 multipath 2 round-robin 2 0
/dev/sdc /dev/sde round-robin 2 0 /dev/sdd /dev/sdf

ia64g:~# dmsetup status
600508b40001045d0001c00006de0000: 0 209715200 multipath 2 2 0 8:32 A 1
8:64 A 1 2 0 8:48 A 1 8:80 A 1

Does anyone have any suggestions as to how to get multipathd to
automatically act on the LOOP UP event?

Hey they are talking about that on linux-scsi right now. http://marc.theaimsgroup.com/?l=linux-scsi&m=108564273619016&w=2
http://marc.theaimsgroup.com/?t=108573124200003&r=1&w=2



I running on kernel 2.6.6 on IA64 with 2.6.6-udm1 device mapper patchset with v0.2.0 of the multipath tools. The HBA is using QLogic Fibre Channel HBA Driver: 8.00.00b11-k and the storage targets are dual Compaq HSV110s.


Cheers,


Guy Coates



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