Adding (removing) disks to a RAIDZ means redistributing all the data in the pool across the new set of drives (adding a drive, or freeing up a drive if enough space is available).
That would be difficult to do correctly, especially since it would be slow enough that most folks would want to be able to continue using the pool while that was done, and without too much performance impact. So it probably has to treat itself as if it's in at least two parts (old layout and new layout) plus whatever it's working on at the moment. I think for example Veritas Volume Manager can do something a little like that, re-arranging storage in place. I haven't looked recently, but it wouldn't surprise me if even that has limitations as to the sorts of in-place rearrangements it can do. And in my experience, while VxVM can be very good when everything works, it's rather complicated to use and an absolute nightmare when things don't work; and it can sometimes be less robust in the face of hardware failures than one might hope or reasonably expect. And of course VxVM isn't free (well, there _have_ been scale limited free promos from time to time). Nor, beyond a certain point, would it be a good idea to add drives to an existing RAIDZ even if it were possible. AFAIK, you can: * replace all the drives, one at a time, with larger drives * add an entire 2nd RAIDZ (i.e. a set of three or more drives) to a pool Given a little foresight (and unless one is trying to do stuff on the extreme cheap), how many situations are there really that _need_ the additional option? Even if there were a "bounty" or some market mechanism like it, would there be enough demand to pay for not only the initial development, but also the _maintenance_ of such a capability? "bounties" may be a useful concept (although more difficult in a regulated corporate-sponsored environment than in a 100.00% community-driven environment, which is why I wonder if they will ever happen except in an isolated adjunct process), but I don't know that this would be a good test case for them. -- This message posted from opensolaris.org _______________________________________________ opensolaris-discuss mailing list [email protected]
