Hello,
I am currently using the dm-multipather (multipath-tools) to allow high-availability / increased capacity to our Equallogic iSCSI SAN. I was wondering if anyone had come across a way to re-instantiate a failed path / paths from a multipath target, when the backend device (iscsi initiator) goes away.
All goes well until we have a lengthy network hiccup or non-recoverable iSCSI error in which case the multipather seems to get wedged. The path seems to get stuck in a [active][faulty] state and the backend block device (sdX) actually gets removed from the system. I have tried reconnecting the iSCSI session, after this happens, and get a new (different IE: sdg vs. sdf) backend block level device, but the multipather never picks it up / never resumes IO operations, and I generally have then to power cycle the box.
We have anywhere from 2 to 4 iSCSI sessions open per multipath target, but even one path failing seems to cause the whole multipath to die. I am hoping there is a way to continue on after a path failure, rather than the power cycle. I have tried multipath-tools 0.4.6/0.4.7/0.4.8, and almost every permutation of the configuration I can think of. Maybe I am missing something quite obvious.
Working Multipather
<snip>
mpath89 (36090a0281051367df57194d2a37392d5) dm-4 EQLOGIC ,100E-00
[size=300G][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=2][active]
\_ 5:0:0:0 sdf 8:80 [active][ready]
\_ 6:0:0:0 sdg 8:96 [active][ready]
</snip>
Wedged Multipather (when a iSCSI session terminates) (All IO queues indefinitely)
<snip>
mpath94 (36090a0180087e6045673743d3c01401c) dm-10 ,
[size=600G][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=0][enabled]
\_ #:#:#:# - #:# [active][faulty]
</snip>
Our multipath.conf looks like this:
<snip>
defaults {
udev_dir /dev
polling_interval 10
selector "round-robin 0"
path_grouping_policy multibus
getuid_callout "/lib/udev/scsi_id -g -u -s /block/%n"
#prio_callout /bin/true
#path_checker readsector0
path_checker directio
rr_min_io 100
rr_weight priorities
failback immediate
no_path_retry fail
#user_friendly_names no
user_friendly_names yes
}
blacklist {
devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st|sda)[0-9]*"
devnode "^hd[a-z][[0-9]*]"
devnode "^cciss!c[0-9]d[0-9]*[p[0-9]*]"
}
devices {
device {
vendor "EQLOGIC"
product "100E-00"
path_grouping_policy multibus
getuid_callout "/lib/udev/scsi_id -g -u -s /block/%n"
#path_checker directio
path_checker readsector0
path_selector "round-robin 0"
##hardware_handler "0"
failback immediate
rr_weight priorities
no_path_retry queue
#no_path_retry fail
rr_min_io 100
product_blacklist LUN_Z
}
}
</snip>
Thanks for your help.
- Mike Vallaly
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