Dear All,
I have configured multipathing on my linux server for two luns coming from the hitachi storage
the output of multipath -ll is as follows:
multipath -ll
mpathc (360060e800562cf00000062cf0000092d) dm-1 HITACHI,OPEN-V
size=50G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 3:0:0:1 sdc 8:32 active ready running
`- 1:0:0:1 sde 8:64 active ready running
mpathb (360060e800562cf00000062cf0000091b) dm-0 HITACHI,OPEN-V
size=50G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 3:0:0:0 sdb 8:16 active ready running
`- 1:0:0:0 sdd 8:48 active ready running

In the /dev/mapper
the paths are as follows:
ls -rlt /dev/mapper/
total 0
crw-rw----. 1 root root 10, 58 Jul 10 13:32 control
lrwxrwxrwx. 1 root root 7 Dec 29 16:41 mpathc -> ../dm-1
lrwxrwxrwx. 1 root root 7 Dec 29 16:41 mpathcp1 -> ../dm-2
lrwxrwxrwx. 1 root root 7 Dec 29 16:41 mpathb -> ../dm-0
lrwxrwxrwx. 1 root root 7 Dec 29 16:41 mpathcp5 -> ../dm-3
lrwxrwxrwx. 1 root root 7 Dec 29 16:41 mpathbp1 -> ../dm-4
lrwxrwxrwx. 1 root root 7 Dec 29 16:41 mpathbp5 -> ../dm-5

I have to combin the two luns to create one one using LVM,which paths should i use

And please explain the role of the grouping in
path_grouping_policy parameter and which one is better to use multibus or failover

And what failback method should I use

Regards
Rafi Ahmad

The settings you are referring to really depend on some of your backend equipment. Your multipath output shows that you are running round-robin at the moment. Different hardware vendors want different settings for their arrays. Consult your hardware manufacturers data for specifics.

Keep in mind that the manufacturers specifications may not always be the best for your environment and may have to be tuned somewhat.

The link below has some good information on the path_grouping_policy as well as what some of the settings mean.
http://www.centos.org/docs/5/html/5....e_devices.html

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