[dm-devel] Multipath failover issues

[Chandra Seetharaman]

On Mon, 2009-03-16 at 21:51 +0530, dushyanth.h at directi.com wrote:
> Hi guys,
> 
> Iam using dm-multipath for a Infortrend dual controller F16F-R4031-6 FC
> system.
> 
> Version details are :
> 
> device-mapper-multipath-0.4.7-17.el5
> device-mapper-1.02.24-1.el5
> device-mapper-event-1.02.24-1.el5
> 
> OS : Red Hat Enterprise Linux Server release 5.2 (Tikanga)
> Kernel : 2.6.18-92.1.10.el5 #1 SMP x86_64 x86_64 x86_64
> 
> Recently, one of the RAID controllers failed and caused multipath to
> fail both active paths
> 
> device-mapper: multipath: Failing path 8:32.

8:32 has failed here.
> sd 2:0:0:0: SCSI error: return code = 0x00020000

error code 20000 mean the BUS is busy.

> end_request: I/O error, dev sdd, sector 1976776672
> device-mapper: multipath: Failing path 8:48.

and 8:48 failed because of that.

Do you know which one was supposed to fail when the RAID controller
failed ? (my guess is it is 8:32).

looks like for whatever reason the other SCSI bus became busy.
> sd 2:0:0:0: SCSI error: return code = 0x00020000
> end_request: I/O error, dev sdd, sector 1967432880
> sd 2:0:0:0: SCSI error: return code = 0x00020000
> end_request: I/O error, dev sdd, sector 161647296
> 
> This caused the ext3 filesystem to go into a read only mode. Full IO
> errors is at http://pastebin.com/m103325d9
> 
> The dual controller storage unit and the host server (Only 1 Server
> using 2 Qlogic FC HBAs) are hooked upto two different Qlogic SanBox FC
> switch for redundancy.
> 
> multipath.conf : http://pastebin.com/m4c7da817
> multipath -v4 -ll : http://pastebin.com/m7d863925
> 
> I have checked the logs on the FC switch and the HBAs
> and i dont see any event which suggest both paths failed at once. Even
> the errors i captured out of dmesg show that one of the physical disks
> that makes up dm-0 had 'end_request: I/O errors' while the other did not
> have any such error.
> 
> sd 2:0:0:0: SCSI error: return code = 0x00020000
> end_request: I/O error, dev sdd, sector 1967432880
> sd 2:0:0:0: SCSI error: return code = 0x00020000
> end_request: I/O error, dev sdd, sector 161647296
> 
> At this point iam wondering how paths 8:32 and 8:48 failed together -
> considering both paths are through two different FC switches. Any
> suggestions on this ?
> 
> Additionaly, I have looked at the mailing list archives & annotated conf
> files and found two options a) failback and b) no_path_retry. What would
> be the best recommended values for these on a dual controller setup like
> mine ?
> 
> It would also be helpful if someone could share infotrend specific
> settings multipath settings.
> 
> TIA
> Dushyanth
> 
> 
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