moving space between lvols in volume group

[OldSchool]

i've a volume group that contains two lvols that are badly allocated. lvol1 has 7GB more space than it needs, while lvol 2 needs to be expanded.

i know i can reduce the space in lvol1 and add it to lvol2, backing up lvol1 before doing so. is there much of a chance that the reduce will leave the data intact on lvol1, or can i pretty much count on needing to restore it as well? is there an easy way to determine if the volume needs restored?

I'm just trying to figure the amount on time i'll need for maintenance.

(I thought about perhaps using "find" and "cksum", comparing before and after.

Any thoughts on the matter?
Thx...

[Pete Randall · Accepted solution]

You wouldn't happen to have OnlineJFS, would you? That could make this a trivial process.

Without OnlineJFS, I suspect the chances of not clobbering your data would be somewhere between slim and none.


Pete

[James R. Ferguson]

Hi:

If you have a filesystem that is contained in the logical volume that you want to reduce; and it is a VxFS filesystem; and you have OnlineJFS, then you may be able to shrink the filesystem *first* with 'fsadm'. Then, if this is successful, you can 'lvreduce' the logical volume container accordingly.

Given the above, however, you should still backup your filesystem as insurance before you begin.

The above procedure would mean no "downtime" other than one for the filesystem backup. I would do that with 'fbackup'.

Regards!

...JRF...

[Jeff Schussele]

Well....you *must* have OnLineJFS to do any reduces/extends without unmounting the filesystems.
But even then you'll find that you have a less than optimum chance of the reductions succeeding without incident.
Seems to be a hit or miss thing for me even when only ~30% of the filesystem is used.
You should attempt several defrags before trying but you should definitely have backups (several) of the filesystem you're trying to reduce.
The extensions should always go w/o incident.

My 2 cents,
Jeff

[OldSchool]

Sorry...forgot to mention, no Online JFS, its gonna have to be the unmount / make change / remount deal. (Thats why I need to schedule a maintenance window.)

They keep telling me they are gonna retire this thing, but its still here (6 proc K-260 and 11.0....yep, i know it needs replaced)

Thx to all, as you confirmed what I thought was happening.