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I have a new F630 with 4 shelves (2 pairs) or about 200GB of disk space. Ideally, I would like to configure it with two 100GB RAID groups composed of 12 data drives, one parity, and one spare each (maybe only one spare for the entire filer).

If I remake the filesystem with half the disks and start using it, will I be able to upgrade to multi-RAID/multi-volume and add the other half of the disks without a backup/restore cycle?

Is there anything else I should know about trying this?

It would work. Any spares before such an upgrade would still be spares after, at which point you could do whatever you want with them.

...and spares will be per-*system*, not per-RAID-group (i.e., it won't be "one spare each"; if you have two RAID groups, and two spares, and a disk fails in one of the RAID groups and one of the spares replaces it, the remaining spare will - if not added to a file system - replace whichever drive fails next, *regardless* of the RAID group the failed disk is in).