[dm-devel] info on enabling only one path with rdac and DS4700

[Gianluca Cecchi]

Hello,
with RH EL 5.7 x86_64 and updates:
# uname -r
2.6.18-274.7.1.el5
# rpm -q device-mapper-multipath
device-mapper-multipath-0.4.7-46.el5_7.1

I'm on a IBM HS21 blade connected to a DS4700 storage array.
Without doing nothing in multipath.conf but blacklisting the internal
disk, I get this kind of configuration:
# multipath -l
mpath1 (3600a0b80005012440000093e4a55cf33) dm-6 IBM,1814      FAStT
[size=3.4T][features=1 queue_if_no_path][hwhandler=1 rdac][rw]
\_ round-robin 0 [prio=0][active]
 \_ 3:0:0:1 sdb 8:16  [active][undef]
 \_ 4:0:0:1 sdc 8:32  [active][undef]
\_ round-robin 0 [prio=0][enabled]
 \_ 3:0:1:1 sdd 8:48  [active][undef]
 \_ 4:0:1:1 sde 8:64  [active][undef]

Is there any config option I can force to use only one path at a time
in the active controller, instead of two (sdb and sdc in my case) in
round robin as I see in iostat?

Also, I noticed that output with "-ll" shows "200" as priority of
paths for the active controller, while "-l" shows 0 for both (see
above)...
Is this a bug or expected difference due to command different switch/verbosity?
(I see similar behaviour also with another server connected to a
DS6800 storage array)
# multipath -ll
mpath1 (3600a0b80005012440000093e4a55cf33) dm-6 IBM,1814      FAStT
[size=3.4T][features=1 queue_if_no_path][hwhandler=1 rdac][rw]
\_ round-robin 0 [prio=200][active]
 \_ 3:0:0:1 sdb 8:16  [active][ready]
 \_ 4:0:0:1 sdc 8:32  [active][ready]
\_ round-robin 0 [prio=0][enabled]
 \_ 3:0:1:1 sdd 8:48  [active][ghost]
 \_ 4:0:1:1 sde 8:64  [active][ghost]

I would like to use default multipath instead of LSI provided rdac, found at
http://www.lsi.com/sep/Pages/rdac/ds4000.aspx
version 09.03.0C05.0504 ,  dated	7/18/2011 with:
New linux kernel versions supported with this release:
             - SLES 10-SP3: 2.6.16.60-0.54.5
             - SLES 10-SP4: 2.6.16.60-0.85.1
             - SLES 11.1  : 2.6.32.12-0.7
             - RHEL5-u5   : 2.6.18-194
             - RHEL5-u6   : 2.6.18-238
             - RHEL6      : 2.6.32-71

In fact I'm using  2.6.18-274.7.1.el5 that is not listed...
Any known cons in using device-mapper-multipath with IBM,1814?

Thanks in advance,
Gianluca