+-- jeff.mohler@netapp.com once said: | If you were my customer and I had to do this..I would use vol copy.
We have done this before, and we used the following method. Note that we are in a mostly read environment - if you're doing more writing than we are, then this might be more painful for us.
0. Set up the volume on the new filer however you like (it has to be as big or bigger than the current vol to use vol copy, even if the vol is mostly empty). Change your fstabs on the machines using the volume to point to the new location. Export the new volume in the same manner as the current volume.
1. Re-export the current volume read-only (writes will fail - we did this during a maint. window and the impact was minimal for us).
2. Use 'vol copy' to copy the volume to the new machine. This is fairly quick when compared to some of the other methods (i.e. tar, dump/restore).
3. Once the vol copy is done, reboot (or simply remount - for us rebooting was easier) the boxes so they pick up the new mount point.
4. Confirm the old filer is no longer serving data, and you're done.
I'd also suggest checking out ndmpcopy.
Oz