[Bug 1540407] [NEW] multipathd drops paths of a temporarily lost device

[Launchpad Bug Tracker]

You have been subscribed to a public bug:

== Comment: #0 - Thorsten Diehl <thorsten.diehl at de.ibm.com> - 2016-02-01 08:57:28 ==
# uname -a
Linux s83lp31 4.4.0-1-generic #15-Ubuntu SMP Thu Jan 21 22:19:04 UTC 2016 s390x s390x s390x GNU/Linux

# dpkg -s multipath-tools|grep ^Version:
Version: 0.5.0-7ubuntu9

# cat /etc/multipath.conf
defaults {
    default_features "1 queue_if_no_path"
    user_friendly_names yes
    path_grouping_policy multibus
    dev_loss_tmo 2147483647
    fast_io_fail_tmo 5
}

blacklist {
    devnode '*'
}

blacklist_exceptions {
    devnode "^sd[a-z]+"
}

---------------------------------------
On a z Systems LPAR with a single LUN, 2 zfcp devices, 2 storage ports, and the following multipath topology:

mpatha (36005076304ffc3e80000000000003050) dm-0 IBM,2107900
size=1.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 0:0:0:1079001136 sda 8:0  active ready running
  |- 0:0:1:1079001136 sdb 8:16 active ready running
  |- 1:0:0:1079001136 sdc 8:32 active ready running
  `- 1:0:1:1079001136 sdd 8:48 active ready running

I observed the following:
When I deconfigure one of the two zfcp devices (e.g. via chchp -c 0, or directly on the HMC), the multipathd removes the two paths via these devices from the pathgroup after 10 seconds. When the zfcp devices comes back, it runs through zfcp error recovery and is being set up properly, and also the mid layer objects are looking fine. However, the multipathd does not add them to the path group again.

Expected behaviour: multipathd does not remove the paths from topology
list, but holds them as "failed faulty offline" until dev_loss_tmo
timout is reached (which is infinite here).

I discussed this already with zfcp development, and it looks most likely
as a problem with multipathd, rather than zfcp or mid-layer.

Easy to reproduce: you need two zfcp devices, one LUN, and preferably
two ports on the storage server (WWPNs). Configure LUN via 2 zfcp
devices * 2 WWPNs = 4 paths.

This can be also reproduced on a z/VM guest. Instead of configuing the
CHPID off, just detach one zfcp device and re-attach it after 30....60
seconds. Same problem.

** Affects: multipath-tools (Ubuntu)
     Importance: Undecided
     Assignee: Skipper Bug Screeners (skipper-screen-team)
         Status: New


** Tags: architecture-s39064 bot-comment bugnameltc-136376 severity-high targetmilestone-inin1604
-- 
multipathd drops paths of a temporarily lost device
https://bugs.launchpad.net/bugs/1540407
You received this bug notification because you are a member of Ubuntu Foundations Bugs, which is subscribed to multipath-tools in Ubuntu.