Aaron Sherman ajs@ajs.com writes:
We've accidentally added our spare disk to a volume. Our OEM says that this is irrevokable, and that we'll have to copy the volume to another disk tray, rebuild the volume and copy back in order to fix this. Is that true? Is there no way to shrink a filesystem and remove a disk once it's been added?
It seem contrary to the ultra-flexible spirit of the Filers....
etraitel@yahoo.com (Eyal Traitel) writes:
It would be lovely if there was such a RAID-filesystem... If anyone have heard of such - share with us...
Well, there surely isn't any real difficulty in principle. It would be rather easier to implement for NetApp's RAID 4 than for some other RAID systems (easy to add a disc => easy to remove it again ...). It would go something like this:
1. A command to start "draining" one or more data discs in a volume. Filing system blocks would not get allocated on them after this. The logical size of the filing system immediately goes down to a value based on the non-draining discs.
2. Proactively move blocks allocated on the draining discs to new locations: this would be done by a sort of dummy "modification" of them. Again this would be easier with WAFL than with many other filing systems.
3. When there are no allocated blocks on the draining discs, set their contents to zero, correcting the parity disc as one goes along. One could start on this before all blocks were deallocated, of course.
4. Now, just shrink the RAID group and return the drained and zeroed discs to the spare pool.
Chris Thompson University of Cambridge Computing Service, Email: cet1@ucs.cam.ac.uk New Museums Site, Cambridge CB2 3QG, Phone: +44 1223 334715 United Kingdom.