On Wed, January 7, 2009 19:34, Billy wrote: > Assuming your free space on the pool is more than 1/[x-1] [1/4 for > our example] > > wouldn't it be very nice to ask zfs to recalculate it's parity and > resilver all the drives to the new state? > > Is that posible?
In theory, of course. You'll notice that very few RAID implementations support anything like that, and those that do are nearly all expensive high-end setups (that are much more complicated to administer than Solaris, too). The Drobo is the only cheap device I know that supports it. This is why I built my NAS as two mirror pairs, rather than a 4-way raidZ. I started with one mirror pair, then added a second pair when I needed the space, and will be able to increase the size of one of the pairs by replacing only two drives when it comes time to increase the size again. I've got more redundancy than a RAIDZ, of course, meaning more safety but also more cost. I decided disk was cheap enough that I didn't mind the cost, and I needed the flexibility. Your mileage may vary. (I have 6 SATA ports on the mobo and two are used for the root disk pool; I actually have two hot-swap bays that aren't wired to controllers; if I found a way to use some of the other controllers on this mobo or added a controller card I could put in a third pair before I needed to upgrade an old pair. If I'd had access to all 8 hot-swap bays from day 1 (I started with only *4* because of limitation on the drivers in older versions) I might have used a root mirror plus two 3-disk RAIDZ groups.) -- David Dyer-Bennet, dd-b at dd-b.net; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info
