EVA - New Configuration

[Uwe Zessin]

Karthik,

I need to do some cleanup of my office and that is best done when I don't get disturbed ;-) What is _your_ excuse?

Secure Path V3.0C is OK. Older versions had some limitations and required special treatment. That's why I was asking.

About your path 'problem' - unfortunately you simply cannot do I/Os to one LUN through all 4 host ports. Let me try to explain how the EVA works:

You have 2 controllers (A/B) or Top/Bottom. Each controller has 2 fibre channel host ports (FP1/FP2). Each controller's ports should be connected to different fabrics for redundancy.

Now, on the EVA only one controller is really managing the characteristics of a LUN. These are the two paths that you are seeing as 'active'. You can only do I/Os to those 2 paths. The other controller, of course, must respond to LUN inquires so that SecurePath knows that there are 2 more paths available where it can switch to in case of a problem.

A 'failover' of the LUN to the other contoller can be done by sending a SCSI 'Start Unit' command. (The HP Tru64 Unix operating system has multipathing embedded and the system administrator must use a special SCSI diagnostic programm to send 'Start UNIT'). My guess is that the 'spmgr select' command uses this mechanism, too.

Perhaps you are somewhat familiar with the VA7xx0 series storage arrays from the, so called 'pre-merger HP' storage business. Here you _can_ do I/O to all controller ports, however, it is my understanding from reading the documentation that in reality the VA works the same way as the EVA. It is just that the controller that does not manage that particular LUN 'reroutes' the I/Os over an internal bus system to the other controller. You are putting an additional burden on the other controller and the internal bus.

Your IOSCAN ouput is a bit hard to read, because multiple spaces obviously get compressed. Please post it as an attachment in the future, thanks!

Anyway, lets take a look at it:

"ctl 19 1/0/8/0/0.1.1.0.0.0.0 sctl CLAIMED DEVICE HP HSV100"
That is the 'LUN 0' I have already been talking about.

"hsx 0 1/0/8/0/0.1.1.0.0.0.1 hsx CLAIMED DEVICE HP HSV100"
That is one path of a real virtual disk from the EVA which has not gone yet through SecurePath (see page 20 and 21 of the Installation Guide, AA-RR4VE-TE).

"disk 15 255/255/0/0.0 sdisk CLAIMED DEVICE HSV100 HP"
"/dev/dsk/c26t0d0 /dev/rdsk/c26t0d0"

I currently don't have access to a HP-UX system to check, but I'd say that this is a disk presented through SecurePath. Use this device for access.

For managing paths it is absolutely necessary that you become familiar with the 'spmgr' utility. See 'Understanding LUN/Path Instance Numbering' beginning on page 58. It looks a little bit different from your outputs, because they used an HSG80-based storage system, but I am sure you get the idea.

If not, ask and give us the chance to earn some more points ;-)

[Karthik S S]

Well, I came office because I had to install some DL580s with M$ Windows :-( ...

And thanks for that those nice explanations. Infact in the other posting I have attached the ioscan and spmgr outputs. So can I assume that whatever starts with hsx in the ioscan output is nothing but a vDisk?? I have created 3 Vdisks on the EVA but have presented only one to the HP-UX. Hence in the ioscan -f output 3 paths are starting with hsx and in the ioscan -fnC disk output only one device is visible ... I think I am getting it right now.

It is interesting to know all the io happens only through one controller ..!!! Then what is the fun of having another controller (unless otherwise the controller 1 fails ) .. Is it possible to spread a bunch of vDisks on controller 1 and the rest to controller 2?? I think it should be possible with spmgr. I need to do a lot of reading :-( and I hate reading those PDFs with 100s of pages due to which often I get in to trouble :-) ...

Anyways thanks and enjoy the weekend (!!) ...

-Karthik S S

[Uwe Zessin]

Oh, my apologies! I have missed that little attachment sign and when you wrote 'attaching' I thought you meant the contents of the next message!


Karthik, in file 'ioscan-f.wri' I count 4 'hsx' devices, not 3. Yes, they are LUNs that have come through the 'hsx driver' - see page 20+21. Sorry for sending you all over that document, but I beleive it's a gold mine.

(Hey, if you are looking for a _large_ manual, then use AA-RS24B-TE. It is the fabric OS reference guide with 725 pages ;-)

The output from ' ioscan -fnC disk' apparently shows a single device, yes - that is correct, if you have presented only one Vdisk from the EVA. The path managment is done by Secure Path which is shielding it from the upper layers in HP-UX. You don't use 'pvlinks' or however it is spelled correctly - I think you understand what I mean. As you can see Secure Path just create a new controller/target/lun combination (/dev/dsk/c26t0d0) to keep HP-UX happy.


"It is interesting to know all the io happens only through one controller ..!!!"

Ahem, it looks I was a bit ambiguous - let me rephrase my sentence:
"Now, on the EVA only one controller is really managing the characteristics of a _single_ LUN". You can (and should) spread all your LUNs over both controllers to make fully use of their computing capacity and cache memory. You can even spread the LUNs from a single disk group over both controllers, which is not possible with the VA. Depending on the model it has only 1 or 2 'redundancy groups' (RG1/RG2) and one controller manages one RG at a time.

I understand it takes some time to get used to Secure Path - I have first worked with it in 1999(!) on Windows NT on Alpha(!) where we had a nice GUI and could use drag&drop for path management. Details, however were much more limited.

[Karthik S S]

Thanks a lot Uwe ...!!

yeah I am familiar with VA, as you said it has 2 RGs and during the creation of LUNs you can which define which RG is going to manage that particular LUN.

And I will go thru the docs somewhere in the evening when I have the time .. I am running through a tight schedule as we have received couple of DL580s with MSA1000 arrays ... dont be to surprised if you a see a new thread popping up in the forums reading "MSA1000 - new Configuration" ;-) ....

I had (yet) another question ...

"As you can see Secure Path just create a new controller/target/lun combination (/dev/dsk/c26t0d0) to keep HP-UX happy."

Does it mean that without securepath there is no way that HP-UX can access these devices???

By the way, what is the time now in Germany? I am asking because you seem to be online 24hrs a day watching the forum ...!!! It is 2PM now in Bangalore, India ...

Thanks,
Karthik S S

[Uwe Zessin]

Karthik,
you can access an EVA without SecurePath from HP-UX provided that there is only one path to the LUN (only one fibre channel adapter is allowed to see that LUN through only one EVA port - that requires proper zoning on the FC switch).

Germany is currently at UTC +1 hour and no, I don't watch 24 hours. It is easy to hit the [reload] button in-between and see if new messages have come up. Also, I have internet connectivity from home. Sometimes I just need a little diversion and ITRC looks like a pleasent place with nice people.

Have fun with those MSAs! They are again somewhat different that the EVA and the VA.

[Karthik S S]

Hi Uwe,

Since you are a ASE pl. answer my question when you find time at,

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=437889

Thanks,
-Karthik S S

[Karthik S S]

Thank you Uwe and watch this thread,

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=465827

-Karthik S s