topic Re: qlogic HBA rescan in Operating System - Linux

qlogic HBA rescan

MartyB — Thu, 13 Aug 2009 18:18:45 GMT

The utility that QLogic provides to rescan the SCSI bus for new devices interrupts IO on all active devices for a short period of time. Is there any way to scan the bus without interrupting IO?

Re: qlogic HBA rescan

Ivan Ferreira — Thu, 13 Aug 2009 19:22:29 GMT

Can you describe the procedure you used? There are different methods to do it and I want to know which one you are using.

Re: qlogic HBA rescan

MartyB — Thu, 13 Aug 2009 19:27:37 GMT

I'm using the tool QLogic recommmends, ql-dynamic-tgt-lun-disc.sh (version 2.3)

Re: qlogic HBA rescan

Ivan Ferreira — Thu, 13 Aug 2009 20:04:35 GMT

I was unable to download the package and check the script. Yo can try the following procedure:

http://run.tournament.org.il/hot-adding-san-lun-to-linux-rh-with-qlogic-drivers/

And the rescan-scsi-bus.sh script. If the server is HP, you can try the hp_rescan command.

Post your results.

Re: qlogic HBA rescan

MartyB — Thu, 13 Aug 2009 20:46:08 GMT

That article refers to the rescan method used in /proc, which has been obsolete since somewhere in the early RHEL4 days. I'm running RHEL5.2 on the system in question, and the QLogic utility is more or less a shell that employs the more modern SCSI scan method of "echo 1 > /sys/class/fc_host//issue_lip" (as opposed to messing around in /proc).

Unfortunately, the "issue_lip" does indeed interrupt IO on my other active LUNs on this host for ~10-15 seconds, which is unacceptable in my environment.

Do you or anyone else know of a method to rescan without IO interruption? These are HP servers (EMC storage), but the version of hp_rescan I've got uses the /proc method as well, and as such is obsolete (I've tried it and it doesn't seem to do much of anything). Can you point me to the latest version? I would certainly give it a shot.

Thanks!

Re: qlogic HBA rescan

Ivan Ferreira — Fri, 14 Aug 2009 01:57:52 GMT

Issuing a LIP will indeed produce a small disconnection on the fabric. Just check these documents:

http://kbase.redhat.com/faq/docs/DOC-3942

You will see that the /proc is still a valid method.

Re: qlogic HBA rescan

Jimmy Vance — Fri, 14 Aug 2009 04:16:52 GMT

Your corect RHEL 5.x switched from /proc to using /sys

HP has a utility caled hp_rescan that is in the hp-fibreutils package in the Linux PSP. The current PSP doesn't have a version that will install on RHEL5, but there is a version posted that is for RHEL5. This works with both QLogic and Emulex HBA's. The latest version is

Linux inbox driver enablement kits for QLogic HBAs and mezzanine cards

http://h20000.www2.hp.com/bizsupport/TechSupport/SoftwareDescription.jsp?lang=en&cc=us&swItem=co-69719-1&jumpid=reg_R1002_USEN

The hp_rescan utility is in the fibreutils-3.0-3 rpm file

hp_rescan -h will give you the syntax and options for use.

Re: qlogic HBA rescan

MartyB — Mon, 31 Aug 2009 14:43:06 GMT

The new hp_rescan does indeed do what I need it to do, thanks!