SAN migration question

[Hilary Nicholson]

Hi,

I'm very new to SANs and am going to be involved in migrating a number of small SANs into one large SAN.
I believe that when the servers and storage (EVAs) are plugged into the new switch the hardware paths (and therefore disk devices) will change.
Someone has mentioned using persistent fibre channel IDs. Does this mean that the hardware paths (and disk devices) will be the same on the new SAN as on the old SAN?

Thanks in advance.

Hilary

[Ivan Ferreira]

In some operating systems, when hardware device will change, on others, the hardware device is bound to the UNIT WWID. What is your operating system?

[Hilary Nicholson]

Hi,

I should have said - it's HPUX 11i. There will be windows servers attached at some point, but they're not my concern :-)

[Uwe Zessin]

OK, then you are affected - would be less of a problem if you were responsible for Windows ;-)

HP-UX uses the Fibre Channel address (other names are: PID, FCID, ...) within its hardware path. It might not be that bad if your servers are using Secure Path for Active/Passive controllers (=EVA-3000/5000). In that case, Secure Path does a persistent binding based on the virtual disk's LUN WWN and to a pseudo device on a new controller.

[Ivan Ferreira]

Yes, devices files will change, you can get more information in these threads:

Use vgexport/vgimport suggestions:
http://forums1.itrc.hp.com/service/forums/bizsupport/questionanswer.do?threadId=205297
http://forums1.itrc.hp.com/service/forums/bizsupport/questionanswer.do?threadId=969524
http://forums1.itrc.hp.com/service/forums/bizsupport/questionanswer.do?threadId=1031178
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=904632

An interesting pdf here:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=846489&admit=-682735245+1151510124347+28353475

[Gene Dinkey_1]

A good place to start is with the SAN Design Guide here:
http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?contentType=SupportManual&locale=en_US&docIndexId=179911&taskId=101&prodTypeId=12169&prodSeriesId=406734

Since you're on HPUX if any of the switch domain numbers or ports change then the hardware path to the device will change. For filesystems this requires some planning, the basic steps are:
1) Export LVM configurations
2) Clean up old VG's and devices
3) Move the equipment
4) Create devices and re-imports the VG's

Here's a document that outlines it pretty well but I would check with the software team for updated instructions:
http://docs.hp.com/en/B2355-90698/ch05s08.html

Regards

Gene

[Hilary Nicholson]

Thanks for all the replies, but just to clarify one thing.

On the new switches, if the domain ID is the same as the old switches, and the FC IDs are kept the same (I presume that's what persistent FC IDs mean?), then will the hardware path to the LUNS remain the same? And if so, no LVM work to do?

Thanks

Hilary

[Uwe Zessin]

Unfortunately, it is a bit more complicated, because the Domain ID is one byte out of the 3-byte PID/FCID. The other relevant one is the port number, but it might not be enough to plug the storage device in the same port number. At least on Brocade switches you also need to make sure that the PID addressing mode is compatible with the old one.

I'd say that you better prepare to deal with PID/FCID changes.

[Hilary Nicholson]

Thanks - now for one other question.

Is there any software on HP-UX that I can use to interrogate the HBAs to find out what WWNs are connected to them?

Does HP-UX actually use WWNs?

Regards,

Hilary

[Keith C. Patterson · Accepted solution]

fcmsutil /dev/td0

where "dev/td0" is the device file of your HBA,
could be td1, td2, etc

This will give you WWN info.