From: Regis Carlier (regis.carlier@apx.fr)
Date: Tue Sep 24 2002 - 05:51:06 EDT
lots of answers to my question ,
special thanks to
Collins, Robert [Robert.R.Collins@hp.com] , Greg Freemyer
[freemyer@NorcrossGroup.com],
Raul Sossa S. [RSossa@datadec.co.cr], Jim Kurtenbach
[KurtenbachJ@crlcorp.com],
O'Brien, Pat [pobrien@mitidata.com], LHERCAUD@bouyguestelecom.fr ,
visageh@mtn.co.ug, Dr Thomas.Blinn@HP.com [tpb@doctor.zk3.dec.com]
The consensus is that , Yes it's possible but the controllers
must be both rebooted at the same time ...
ps : imho , and it 's written this way in Tru64 documentations , HBA (Host
Bus Adapter) is not specific to Fibre channel but is a generic term .
The Answers :
----- Collins, Robert [Robert.R.Collins@hp.com] :
The HSZ80 will load balance across the physical adapters but both adapters
have the same scsi bus number (as I recall) so you will see no actual
performance gain at the operating system / filesystem level. This is
different than the HSG setup where each adapter is assigned a seperate scsi
bus number so the physical load balance does translate operating system /
filesystem performance increase.
Bob Collins
Unix Business Critical Support Team
Compaq , Part of the New HP
Office: 412-856-2716
Pager: 412-644-2068
Robert.R.Collins@hp.com
----- Greg Freemyer [freemyer@NorcrossGroup.com] :
Regis,
If I understand you, you have multiple units being served by a HSZ80 pair in
Multibus mode.
You have some set to prefer the upper HSZ80, and some the lower HSZ80.
If so, you need to be aware that the preferred_path setting only has effect
if both HSZ80s are reset simultaneously.
If after that, you have a HSZ80 failure and you replace the HSZ80, you will
only get back to a load balancing if you do the dual reset again.
Obviously, during the reset time your array is offline, so this is not a
trivial solution, but it is the only one I know.
HTH
Greg
==============
Greg Freemyer
Internet Engineer
Deployment and Integration Specialist
Compaq ASE - Tru64 v4, v5
Compaq Master ASE - SAN Architect
The Norcross Group
www.NorcrossGroup.com
----- Raul Sossa S. [RSossa@datadec.co.cr] :
SET PREFERED_PATH and load balance as you need before applying the next:
UPPER_HSG80> restart other
UPPER_HSG80> restart this
REMEMBER THAT ALL PARTITIONS OF A UNIT MUST BE CONTROLLED BY THE SAME
CONTROLLER AND THAT THIS PROCESS WILL SHOW DOWN YOUR I/O MOMENTARELY.
ADDITIONALLY, remember that both controllers restart must be done
as fas as possible in order to get the most simultaneous restart.
----- Jim Kurtenbach [KurtenbachJ@crlcorp.com] :
Bottom line is that it works (once) from the initial powerup of the
controller. Unfortunately, I've never found a way to set a unit on a
controller after powerup/controller boot. On OPENVMS, there is a command I
use to select a path for a volume (set $1$dka1: /path=pkb/switch ), haven't
found the equivalent for Tru64. I'd be very interested in what you find
out on this.
----- O'Brien, Pat [pobrien@mitidata.com] :
>From my investigation previoously, true real multipath on a hsz80 requires 4
hba's in the server with one connected to each port. Will be interested in
what others are saying now though.
----- LHERCAUD@bouyguestelecom.fr :
Hello Regis,
I suppose you meaned HSG80 not HSZ80 as you said HBA!
Yes it is possible provided someone takes some actions on the UNIX side.
The problem is the Preferred_Path is used onto the HSG80 only at unit
creation time.
After one HSG80 controller restarts all the units remain attached to the
other controller.
I wrote some scripts/tools to do that. If you want to automate the thing,
you will need to put in place some method to detect that the units moved ...
or just blindly execute the :
"Restore_Paths_Disks_All -exe"
periodically. If the units are in place it will do nothing.
Use the Restore* scripts with the "-exe" argument if you want them to
execute the commands to relocate the units, otherwise the commands will only
be shown on stdout.
Recall to start "Find_Controlers -update" first time and any time you add a
module to your SAN !
PS: I did not include the Unix man pages nor the French message catalogue
for these tools.
Regards,
Lucien HERCAUD
Consultant Systeme UNIX en mission chez Bouygues Télécom
DCSI/DEB/HSI/INL/INX
* Tel. Fixe +33 1 3945 4260 * BOUYGUES Telecom
* Tel. Mobile +33 6 0944 2880 * 24 Avenue de l'Europe
* Fax +33 1 3945 4322 * 78944 VELIZY Cedex
* mailto:lhercaud@bouyguestelecom.fr
----- visageh@mtn.co.ug :
Yes, but both controllers in the HSG80 must be rebooted at the same time.
If one controller fails, or rebooted, the other one will take all the load.
Now when the failed or rebooted controller come online again, it will not
revert back the preferred paths. You must reboot both controllers at the
same time.
That is how it works on Tru64 5.1 and ACS8.5F. Perhaps this has been fixed
in 8.7x.
----- Dr Thomas.Blinn@HP.com [tpb@doctor.zk3.dec.com] :
It's probably a bug in system software. What's SUPPOSED to happen
is load balancing, but it doesn't always work right. Make sure you
have the patches installed (if they don't break your system), but
don't be surprised if the real fix is only available in V5.1A or
V5.1B (perhaps with patches).
Tom
Dr. Thomas P. Blinn + Tru64 UNIX Software + Hewlett-Packard Company
Internet: tpb@zk3.dec.com, thomas.blinn@compaq.com, thomas.blinn@hp.com
110 Spit Brook Road, MS ZKO3-2/W17 Nashua, New Hampshire 03062-2698
Technology Partnership Engineering Phone: (603) 884-0646
ACM Member: tpblinn@acm.org PC@Home: tom@felines.mv.net
Worry kills more people than work because more people worry than work.
Keep your stick on the ice. -- Steve Smith ("Red Green")
My favorite palindrome is: Satan, oscillate my metallic sonatas.
-- Phil Agre, pagre@alpha.oac.ucla.edu
Yesterday it worked / Today it is not working / UNIX is like that
-- apologies to Margaret Segall
Opinions expressed herein are my own, and do not necessarily represent
those of my employer or anyone else, living or dead, real or imagined.
------
ESC:wq
-- Régis Carlier, APX Computer, 31 rue Denis Papin, Parc Club des Prés, 59650 Villeneuve d'Ascq Tel: +33320190018 , Fax: +33320190010 , Gsm: +33686943971 , Mail: Regis.Carlier@apx.fr
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