Swapping Storage Groups, retain LUN ID's

Question

We are trying to swap storage groups (sg) in a masking view. One group is for R2's, the other TGT's. However, we find that in order to do so, we must go through the rather sticky process of deleting the existing view, then re-create the view again with the new sg, and then re-assign the lun id's on at a time, ala:

sample:

symaccess -sid xxxx add -name host_tgt_stor -type storage devs xxx,xxx,xxx -lun 7,8,9

Additionally, this is a process that we would have to perform repeatedly, so in order to revert back to the R2's, we'd have to perform the same steps, only with the originak R2 sg. Finally, these processes must be scripted for repeated use.

Question is, is there any OTHER (less steps) way to swap storage groups while simultaneously retaining LUN ID's? We already know that merely removing the R2 sg and adding back the TGT sg will not work, as this type of swap does NOT retain the same LUN ID's.

dynamox · Answer

could be simpler to move initiator group in and out of multiple masking views ?

RobertDudley · Answer

Can you create two masking views and put them on different FA's then just change zoning?  Have a production zone on FA 7A0/10A0 then a zone to see the R2's on 7B0/10B0?  Just remove the one zone and load the other.

hernster · Answer

Both suggestions are viable, but without testing, does any one know the affect on the original LUN id's? (That is if we either pull the initiator group from the R2 masking view and move it to the TGT masking view OR zone R2's to port 0, then swap zone with TGT's zoned to port1.)  Thanks

dynamox · Answer

LUN numbering should be consistent between the masking views, why is that important to you ? What are you doing on the host side , do you export volume groups, present different devices and re-import ?

Gary_Grubb · Answer

Hi Dynamox, We are currently using the same setup in out DR environment. We have 2 masking views, one for the R2s & one for GClones. We move the host WWNs between IGs of the different masking views depending on where the hosts need to be brought up. This ensures the LUN numbers are constant. We are planning to move to EMCs new cascaded SG feature & have a single masking view & move the child SGs in an out of the parent depending on what the host needs to see. This will not guarantee the same LUN numbers. My question is, is it still important to maintain a constant LUN number? I know the ESX uses eui
aa to identify the LUN. I am not sure about other operating systems & multipathing software. Would appreciate inputs from others as well. Hernan, Which option did you choose finally? Gary.

dynamox · Answer

Gary,

I don't know of an operating system that would care, maybe OpenVMS ? Windows could care less, *NIX rely on volume group header to find and import correct disks (if you let it scan instead of supplying an import file).

Gary_Grubb · Answer

Thank you. That makes sense, we use snaps for backups & those are mounted on different servers through different FAs -so it works with different LUN IDs.

Symmetrix

Swapping Storage Groups, retain LUN ID's

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