topic Re: DM multipath on Linux in Operating System - Linux

DM multipath on Linux

John Guster — Wed, 25 Mar 2009 13:33:24 GMT

How to remove paths under DM multipath management? We have 4 paths for each device, want reduce to 2. Thanks.

Re: DM multipath on Linux

Matti_Kurkela — Wed, 25 Mar 2009 15:07:10 GMT

First disconnect the extra paths or otherwise cause them to stop working (zoning/masking changes in FibreChannel environment?).

Then execute "multipath -f mpathXX" where mpathXX is the name of multipath device whose paths you are reducing, or "multipath -F" to remove all non-functional paths and devices from the multipath tracking at once.

MK

Re: DM multipath on Linux

John Guster — Wed, 25 Mar 2009 15:36:40 GMT

multipath -F does not work, want remove [failed][faulty] path see below:
mpath1 (12345)
[size=10 GB][features="0"][hwhandler="0"]
\_ round-robin 0 [prio=3][active]
\_ 1:0:0:35 sdc 4:32 [active][ready]
\_ 1:0:1:35 sde 4:64 [active][ready]
\_ 2:0:0:35 sdg 4:96 [active][ready]
\_ 2:0:1:35 sdi 4:128 [failed][faulty]

mpath0 (67894)
[size=10 GB][features="0"][hwhandler="0"]
\_ round-robin 0 [prio=3][active]
\_ 1:0:0:0 sdb 4:16 [active][ready]
\_ 1:0:1:0 sdd 4:48 [active][ready]
\_ 2:0:0:0 sdf 4:80 [active][ready]
\_ 2:0:1:0 sdh 4:112 [failed][faulty]

Re: DM multipath on Linux

skt_skt — Wed, 25 Mar 2009 18:45:34 GMT

Paths coming from 1:0 are from one HBA and other two paths from 2:0 which represents another HBA.

so make the masking/zoning changes mention above first so as to have one path each from each of the HBAa.

Re: DM multipath on Linux

Matti_Kurkela — Fri, 27 Mar 2009 06:53:10 GMT

Ah, so the underlying disk devices have not been deleted from the system yet? OK, I see now...

To tell the system that a certain disk device is not going to come back, you should write an "1" to the "delete" pseudo-file in the sysfs directory of that disk device.

In your situation:

echo 1 > /sys/class/scsi_disk/2\:0\:1\:35/device/delete

echo 1 > /sys/class/scsi_disk/2\:0\:1\:0/device/delete

Don't bother to "cd" to the device directory, because that directory will cease to exist immediately after you enter that command.

As far as I've understood, the multipath system should automatically receive a notification of the device deletion. If the multipath command still displays the failed links, try flushing the multipath devices again.

MK

Re: DM multipath on Linux

John Guster — Wed, 01 Apr 2009 14:21:11 GMT

MK,
is scsi_device same as scsi_disk under /sys/...?

Re: DM multipath on Linux

Matti_Kurkela — Wed, 01 Apr 2009 16:40:18 GMT

Why yes, it seems to end up into the same place.

However, I just noticed there is another, even simpler path:

echo 1 > /sys/block/sdh/device/delete
echo 1 > /sys/block/sdi/device/delete

MK

Re: DM multipath on Linux

John Guster — Wed, 01 Apr 2009 17:29:21 GMT

Thanks MK. It helps.