A Multipath Mapping Inconsistency Issue

刘泽宇

现象：
The server has incorrect device mappings.

The /etc/multipath.conf shows following wwid/alias pairs:

multipaths {
(snip)
multipath {
wwid <WWID1>
alias <ALIAS1>
}
multipath {
wwid <WWID2>
alias <ALIAS2>
}
(snip)
}

But "multipath-ll" shows

<ALIAS1> (<WWID2>) dm-22 NETAPP,LUN C-Mode >>> should be <ALIAS2> per setting in multipath.conf
<ALIAS2> (<WWID1>) dm-21 NETAPP,LUN C-Mode >>> should be <ALIAS1> per setting in multipath.conf


原因：
The logs shows multipathd already found the wrong mappings, but with no clue to what happened exactly.

Feb 24 12:07:28 hostname multipathd: <WWID1>: unable to rename <ALIAS2> to <ALIAS1> (<ALIAS1> is used by <WWID2>)
Feb 24 12:07:28 hostname multipathd: <WWID2>: unable to rename <ALIAS1> to <ALIAS2> (<ALIAS2> is used by <WWID1>)


处理方法：
You don't need full outage window, flush the specific mapping and then re-run multipath to trigger re-mapping.

In the example below, we can see the mapping is corrected.

# multipath -f <ALIAS1>
# multipath -f <ALIAS2>
# multipath -ll | egrep "dm-21|dm-22"
<ALIAS1> (<WWID1>) dm-21 NETAPP,LUN C-Mode
<ALIAS2> (<WWID2>) dm-22 NETAPP,LUN C-Mode