Wednesday, October 1, 2008

How To Easily Find The WWN's Of A QLogic HBA On RedHat Linux

Hey there,

Today's post should be nice and simple. Maybe even short... yeah ;) This is a bit of a follow-up on a post we did a long long time ago regarding Linux networking tips. It's quite a bit more specific, but remains true to the spirit of that post (from December 2007, which, still, seems like it was just last year ;)

Today, we're going to take a look at a really simple way to figure out the World Wide Name (WWN) of both your Fibre NIC's port(s) and the switch it's connected to. To add a bit of clarity here, a lot of times you'll hear a QLogic (which is what we have on the menu today) Fibre NIC referred to as an HBA (Host Bus Adapter). It's become common to interchange the meaning of the two, although, technically, the HBA is an I/O adapter that resides "between" the computer's Bus (A collection of wires that data gets transmitted through. Not a clever acronym as far as I know ;) and the Fibre Channel Loop, and deals with the overhead associated with the transfer of information between the two. This becomes even more confusing when you consider that some Fibre NIC cards either have an HBA on board or act in the capacity of an HBA. But, in the end, you have to ask yourself just one question: If you can fix one a' them doohickies when it breaks, who cares? ;)

Anyway, back to the topic of the day: Finding the port and switch WWN's for a QLogic Fibre NIC on RedHat Linux. The version we're testing on today is:

hostess # cat /etc/issue
Red Hat Enterprise Linux ES release 4 (Nahant Update 6)
Kernel \r on an \m

hostess # uname -a
Linux hostess1 2.6.9-67.0.1.ELsmp #1 SMP Fri Nov 30 11:51:05 EST 2007 i686 i686 i386 GNU/Linux

The setup on our machine is a very simple QLogic Fibre Channel Card (which comes with it's own on-board HBA), referred to by the operating system as qla2xxx (This translates to another meta-name in /etc/modprobe.conf, but since that name is an alias for this name, we'll use this one instead.). In order to find out the WWN's for this card, all we need to do is follow this simple process:

1. Find the instance of the card's name in the /proc filesystem:

host # find /proc -type d -name qla2xxx
<-- Note that we referenced a directory here. Normally, you wouldn't know this, but we did, so it made the search go faster by .001 seconds (according to the "time" command which is notorious for being off by a few thousandths of a second every now and again ;)

2. cd into the qla2xxx directory and do an "ls -l" and a "file" on "*" (not really necessary, but fun :)

hostess # ls -l *
-rw-r--r-- 1 root root 0 Sep 30 12:25 1
-rw-r--r-- 1 root root 0 Sep 30 12:25 2
-rw-r--r-- 1 root root 0 Sep 30 12:25 3
-rw-r--r-- 1 root root 0 Sep 30 12:25 4
hostess # file *
1: empty
2: empty
3: empty
4: empty

3. Now, you've probably noticed that the file sizes are all 0 and the output of the file command says "empty" for all of them. This is an illusion the /proc filesystem plays. You can prove this (the long way) by copying any file into, say, /tmp and running the same commands again:

hostess # cp 1 /tmp/DELETEME
hostess # ls -l /tmp/DELETEME
-rw-r--r-- 1 root root 1033 Sep 30 12:27 /tmp/DELETEME
hostess # file /tmp/DELETEME
/tmp/DELETEME: ASCII English text's interesting to note, also, that running the "stat" command doesn't even get you the correct information within the /proc filesystem. The results are the same as above: The file's empty if it's in /proc, but has mass when it's copied or moved out.

4. Now we can get our info. This egrep command pulls out all the salient information. There's a lot more output in each file and, depending upon your interests (or how bored you are right now ;), you might find a lot of it very helpful in a troubleshooting or performance-evaluation situation. First the command, then the explanation:

hostess # egrep 'QLogic|scsi-' *
1:QLogic PCI to Fibre Channel Host Adapter for QLA2342:
2:QLogic PCI to Fibre Channel Host Adapter for QLA2342:
3:QLogic PCI to Fibre Channel Host Adapter for QLA2342:
4:QLogic PCI to Fibre Channel Host Adapter for QLA2342:

The things to notice above, are that only two of the targets have the "scsi-qlaX-adapter-target" value set. This is because the "QLA2342" (qla2xxx's actual name, shown in the output) only has 2 ports (despite the four descriptors). You can actually read up more on the technical specs at QLogic's Official QLA2342 Spec Page. Notice that even "they" refer to the QLA2342 as an HBA, rather than a Fibre Channel NIC...

5. And, now, here's the information you're ultimately looking for. To find the WWN for each of the two "ports," check the egrep results for the files that came back with the word "target" in them. All four use the "port" keyword. You can grab this more succinctly off of the command line with:

hostess # grep -l "target-" *|xargs egrep -i 'QLogic|scsi' /dev/null
2:QLogic PCI to Fibre Channel Host Adapter for QLA2342:
2:Number of reqs in pending_q= 0, retry_q= 0, done_q= 0, scsi_retry_q= 0
2:SCSI Device Information:
2:SCSI LUN Information:
3:QLogic PCI to Fibre Channel Host Adapter for QLA2342:
3:Number of reqs in pending_q= 0, retry_q= 0, done_q= 0, scsi_retry_q= 0
3:SCSI Device Information:
3:SCSI LUN Information:

From the above, you'll know that the "adapter-port-0" line is the WWN of the port itself, and the "target-0" line is the WWN of the Fibre Switch it's connected to.

Simple as binary PI ;)


, Mike

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