You can use the symmask command ..


From the DMX point of view the LUN is mapped on the FA with a "hard" lun .. this is configured in the binfile and you can change it only via binfile (or symconfigure).

If you want to modify how the hosts will see the luns you need to modify the "offset" that the box will apply when answering to host queries. So if your lun is mapped on the FA at "hard" address 5 (lun number 5) you can show it to your host as "soft" lun 0 applying a given offset that will be subtracted from the "hard" lun.

So if you want to present lun number 5 (that is the first and only lun that a given host can see) you'll use

symmask -sid 123 -wwn 10000000abcdef01 -dir 15a -p 0 set lunoffset on 5 0

Obviously 5 is the offset that you want to apply and 0 is the number of luns seen by the host that will have this offset. So zero means "the first lun".

Hope this is useful.

what happens if you already have a lun at the address ? For example i have a lun on the FA that's mapped to Target=0 LUN=5 ...and i take another LUN tha'ts mapped to LUN=6 ..and try to offset it to be LUN 5. What would happen ? I am just trying to see how Symmetrix handles it to prevent human error ?

Thanx,

will give that a try when I'm onsite next week.

Right now I'm unable to answer your question, dynamox .. I think I'll run a couple of tests

I'll show you later !!

Dynamox, unfortunatly while testing the lun offset feature I had some small problems (hmm the host loose completly access to its volumes) ..

My kind and gentle customer tolerated this small disruption (the host wasn't a production server) but I think I won't do any further test.

Please note that I'm quite sure that the "lun offset" feature works well in a simple situation. The tests I was running were a little bit kinky since I was trying to overlap a "soft" lun (generated with the lunoffset for a specific host) to an existing "hard" lun (mapped on the FA and granted to the same host).



-s-

so there was no warning from the Symm side that you are about to overlay hard mapped lun ?

Any news on the subject ??

Dynamox, no warnings .. But maybe I used the wrong base/offset while enabling the lunoffset.. Since I lost all the volumes I think that there was something wrong on the commandline. I think it was my error. I'll run more tests when I'll have a "safe" host that I can play with.

Prior to 5772 code you could use lunoffset, which essentially just skips a certain number of devices for an FA/HBA combination and shifts device numbers by however large your offset is. Note that if you have a device mapped at a lower address than you offset it will no longer be visible to the host, including the VCM device if it is at lun 0.

What you are looking for is dynamic lun addressing, which should behave very similarly to the way masking in the clariion has always worked in that you define an ALU and HLU when you mask.

There are real world scenarios where lunoffset is a pain but until you get to 5772 code there aren't many alternatives.