IBM SAN LUN Resizing

I have an IBM SAN in production.
the whole enclosure is fully populated with drives already.
a couple of disk groups created (RAID5), multiple LUNs are presented to targets.

One of the LUNs are running out of space and I do not have any available space in that disk group.
from another disk group, I have 500GB of unassigned space.

is there any way that I can "de-obligate" that 500GB space from disk group A (RAID5)
and use that to extend the other RAID group and present to a LUN in that group?

help please.
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andyalderSaggar maker's framemakerCommented:
IBM make a lot of different SANs (well they rebadge most of them admittedly) so it's hard to tell for sure but "no" is quite likely to be correct. Can't you just create a new LUN on the disk group that has space and present it to the host as a separate disk and shuffle data around a bit?
Gerald ConnollyCommented:
You could probably do it the hard way, backup data, disolve both RAIDsets and recreate with all available disks, then replay backup
To add to my terse answer ... The whole point of a disk group is to separate them into groups that you slice and dice into LUNS.   If you could add free space from one disk group into another then the whole point of disk groups is lost.  That is why the firmware won't let you do it.

Now a really ugly thing  you could do .... create a lun with the free space in one disk group, and create a lun with free space in another group, and then use host-based RAID0 to stripe them into another lun.  Technically you will be protected, since you'll end up with a hybrid hardware+software RAID50.    

(But best practice, of course, is to add more disks or larger disks .. i expect this is going to be an ongoing problem)

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andyalderSaggar maker's framemakerCommented:
A concatenated drive set would make more sense than RAID0 but either way if it's Windows you have to convert to dynamic which is far from ideal on a SAN. That's why I suggested shuffling data about on an extra drive instead.
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