topic Re: RHEL 5 installer using 4 disks instead of 1 in Operating System - Linux

RHEL 5 installer using 4 disks instead of 1

Randy Hagedorn — Tue, 29 Jun 2010 19:56:37 GMT

Hi,

I'm installing RHEL 5 using and EVA4100 and Linux BL480C. The installer is seeing the one LUN four times as disk drives being available to use, because of multi-pathing. When this system was configured by a VAR, they had to physically remove all paths to the Server except for one, but I don't know how they did it.

The fabric switch is a Brocade.

Any ideas how to do this and what the utilities may be?

Thanks,
Randy

Re: RHEL 5 installer using 4 disks instead of 1

Jan Soska — Wed, 30 Jun 2010 04:43:10 GMT

Hello,
it looks you do not have proper multipath configuration.
Please read my thread at: http://forums13.itrc.hp.com/service/forums/questionanswer.do?threadId=1434303

Jan

Re: RHEL 5 installer using 4 disks instead of 1

Gerardo Arceri — Thu, 01 Jul 2010 02:10:55 GMT

Mnh, that will not do any good during the installation, I suggest you get someone to unplug all fiber cables but one at least until you have the OS installed

Re: RHEL 5 installer using 4 disks instead of 1

Zinky — Thu, 01 Jul 2010 12:06:48 GMT

Yikes!

Be misguided not no more. THERE is an official Redhat document on HOW to install Redhat on a SAN Boot disk with "multipathing enabled" so you avoid that "seeing 4 or 8 LUNS" situation. There should also be no need in yanking cables, etc.

Please peruse and FOLLOW strictly the RedHat recipe here:

http://kbase.redhat.com/faq/docs/DOC-17644

If in your area Redhat had locked access to the KDBs, then you must have a Redhat Accout and the URL is:

https://access.redhat.com/kb/docs/DOC-17644

DO NOT Forget: After you have installed your OS, install/update your device multi pather software to HP's. This is not mentioned in the document I think.

Re: RHEL 5 installer using 4 disks instead of 1

Randy Hagedorn — Thu, 01 Jul 2010 12:46:24 GMT

Thanks for all the valuable answers.

Instead of actually unplugging cables because there aren't any, we used the HP OnBoard Administrator on our HP BladeCenter and EVA and "logically" disconnected the paths from the Brocade SAN switch. Later we will reconfigure the switch back to being multipathed on the SAN.

I wish I knew of Alzhy's answer 10 days ago, because that's when we first ran into the problem. I will definitely keep this procedure in my documentation for the next time.

Thanks,
Randy

Re: RHEL 5 installer using 4 disks instead of 1

Gerardo Arceri — Fri, 09 Jul 2010 03:21:00 GMT

Alzhy:
I was precisely looking for something like that, if the thread was mine i'd give you 10 points for that answer!

Re: RHEL 5 installer using 4 disks instead of 1

Zinky — Mon, 12 Jul 2010 12:38:33 GMT

As an added FYI:

I have seen many Linux Admins (even Vets) "install" or even migrate their local OS env to a SAN Lun using the "drop all other FC paths, except one" approach - and saw it was wrong. Sure the OS works perfectly BUT the SAN OS disk turns out to be NOT multi-pathed.

An easy check IF your SAN OS environment is "properly" on SAN Boot is to simply do:

df -k /boot

it should be mounted on top a multipath device like:

[root@irky01 ~]# df -k /boot
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/mpath0p1 248895 17194 218851 8% /boot

Additionally -- IF your OS filesystems rest on top of LVM, also do:

[root@irky01 ~]# vgdisplay -v vgsan|grep "PV Name"
Using volume group(s) on command line
Finding volume group "vgsan"
PV Name /dev/dm-2

[root@irky01 ~]# multipath -ll
mpath0 (360060e8004753f000000753f00000e0e) dm-0 HP,OPEN-V
[size=52G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=0][active]
\_ 2:0:4:0 sds 65:32 [active][ready]
\_ 0:0:4:0 sdt 65:48 [active][ready]
\_ 6:0:4:0 sdu 65:64 [active][ready]
\_ 4:0:4:0 sdv 65:80 [active][ready]

That ensures your SAN OS disk is indeed Multi-Pathed as well.

HTH for everyone wising to be on SAN Boot.

Alzhy.