[Bug 1020436] Re: Cannot read superblock after FC multipath failover

[Steve Fisher]

Storage devices:

$ sudo lsscsi
[0:0:0:0]    cd/dvd  TSSTcorp CDDVDW TS-L633F  IT03  /dev/sr0
[4:2:0:0]    disk    IBM      ServeRAID M5015  2.12  /dev/sda
[5:0:0:0]    disk    HITACHI  OPEN-V           6008  /dev/sdb
[5:0:0:1]    disk    HITACHI  OPEN-V           6008  /dev/sdc
[5:0:0:2]    disk    HITACHI  OPEN-V           6008  /dev/sdd
[5:0:1:0]    disk    HITACHI  OPEN-V           6008  /dev/sde
[5:0:1:1]    disk    HITACHI  OPEN-V           6008  /dev/sdf
[5:0:1:2]    disk    HITACHI  OPEN-V           6008  /dev/sdg
[6:0:0:0]    disk    HITACHI  OPEN-V           6008  /dev/sdh
[6:0:0:1]    disk    HITACHI  OPEN-V           6008  /dev/sdi
[6:0:0:2]    disk    HITACHI  OPEN-V           6008  /dev/sdj
[6:0:1:0]    disk    HITACHI  OPEN-V           6008  /dev/sdk
[6:0:1:1]    disk    HITACHI  OPEN-V           6008  /dev/sdl
[6:0:1:2]    disk    HITACHI  OPEN-V           6008  /dev/sdm

Zoning:

-  There are two HBAs.  Each HBA is plugged into a separate Brocade DCX switch, and each switch is connected to a different fabric (Fabric A and Fabric B respectively) 
-  The storage array presenting the luns is also directly connected to the same switches, in each Fabric via 4 ports (Array ports 1A,3A,6A,8A -> Fabric A; Ports 2A,4A,5A,8A -> Fabric B).
- Each HBA is zoned so as to see two storage array ports (2 in each fabric).  Basically this means that when I disable the FC port an HBA is connected to, it loses two paths to the lun.

HBA1 -> DCX 1 (Fabric A) -> 3A,6A
HBA2 -> DCX 2 (Fabric B) -> 4A,5A

Blacklisting:

Thanks for pointing this out - (note that I only added in the 'SMART'
vendor/product after the problem initially exhibited - in an effort to
remove the warning regarding a USB flash storage device that appeared in
the multipath -ll output.  It _shouldn't_ be a factor).

Fixed now, initrd updated.  Reboot/testing later today (likely in about
3 hours' time).

$ echo "show config" | sudo multipathd -k
multipathd> show config
defaults {
	user_friendly_names yes
}
blacklist {
	devnode ^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*
	devnode ^hd[a-z]
	devnode ^dcssblk[0-9]*
	devnode ^cciss!c[0-9]d[0-9]*
	wwid 3600605b0039afe20ff000054052e7d38
	device {
		vendor SMART
		product SMART
	}
	device {
		vendor DGC
		product LUNZ
	}
	device {
		vendor IBM
		product S/390.*
	}
}
blacklist_exceptions {
}
--snip

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https://bugs.launchpad.net/bugs/1020436

Title:
  Cannot read superblock after FC multipath failover

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