topic Re: FC HBA & multipath software instalation in 64bit linux (Redhat / Centos) in Operating System - Linux

FC HBA & multipath software instalation in 64bit linux (Redhat / Centos)

Jan Soska — Wed, 09 Jun 2010 12:05:54 GMT

Hello all,
we are familiar with configuring and using FC HBA's (mostly Qlogic) in windows enviroment.

Now we try to install some BL465c proliants with Qlogic HBA and 64bit Centos 5.5.
Is there any guide how to deploy drivers and configure system to efectively use all available paths on SAN (connected to EVA6000 - 4 paths via 2 fabrics)? We are now able to see devices 4 times, so we know there is some multipath problem.

Any help, guidelines welcomed and paid in points.. :)

Jan

Re: FC HBA & multipath software instalation in 64bit linux (Redhat / Centos)

Ivan Ferreira — Wed, 09 Jun 2010 12:57:37 GMT

Check this guide for setting up multipath:

http://www.redhat.com/docs/manuals/csgfs/browse/4.6/DM_Multipath/index.html

Re: FC HBA & multipath software instalation in 64bit linux (Redhat / Centos)

Jan Soska — Wed, 09 Jun 2010 13:11:55 GMT

Hello Ivan,
thanks for your post.

After implementing it - can we use common multipath policy settings like MRU or RR ?

Do you use such setup and are you happy with it?

Jan

Re: FC HBA & multipath software instalation in 64bit linux (Redhat / Centos)

Gerardo Arceri — Thu, 10 Jun 2010 19:29:45 GMT

Jan:

We use DM-Multipath with EMC SYMMETRIX SAN, these settings have give us the best results so far
/etc/multipath.conf

defaults {
udev_dir /dev
polling_interval 2
selector "round-robin 0"
path_grouping_policy multibus
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
prio_callout /bin/true
path_checker tur
rr_min_io 100
rr_weight priorities
failback immediate
no_path_retry fail
user_friendly_names yes
}

As you can see, we chose to use TUR (Test Unit Ready) as the path checker, and round-robin as the grouping policy, that has given us the best mix of performance and reliability.

Re: FC HBA & multipath software instalation in 64bit linux (Redhat / Centos)

Tim Nelson — Thu, 10 Jun 2010 19:52:22 GMT

If you install the DMMultipath kit from HP it will add the latest HP recommended rules to your /etc/multipath.conf.

Also read the release notes that come with as they specify modprobe options that HP recommends for qlogic cards as well..

If you are using qlogic ( not hp rebranded) hbas then I would also download the Linux-Tools from qlogic. supplies rescan and info commands.

You will always see 4 paths.. the multipath.conf either assigns /dev/mpathX or you can configure nice names. e.g. /dev/mapper/eva6000_lun1, /dev/mapper/eva6000_lun2.

Alwasy use the /dev/mpath/mpathX or /dev/mapper/nice-name with LVM or other disk manager, if you simply use one path like /dev/sda or /dev/sdg then you will be using only one path and functionally omitting the multipath abilities.

Re: FC HBA & multipath software instalation in 64bit linux (Redhat / Centos)

Jan Soska — Sun, 13 Jun 2010 07:42:43 GMT

Thanks to all of you guys...

Jan

Re: FC HBA & multipath software instalation in 64bit linux (Redhat / Centos)

Mohan Wickramasinghe — Fri, 12 Nov 2010 16:31:01 GMT

Hi
Interesting. is using

path_grouping_policy multibus
or
path_grouping_policy group_by_prio

i see no difference in performance using multibus, seems to split the load but takes the same amount of time.

in linux, there are not many algorithms implemented for performance. round robin is the only one.
please let me know if this was the optimal multpath.conf
thanks