On Tue, May 12, 2015 at 02:01:54PM +0200, Stefan Priebe - Profihost AG wrote: > Hi, > > while cloud / vms usage become more and more popular and qemu now also > offers memory hot add and unplug, cpu hot add and unplug, we still > suffer from a missing xfs shrink. Over the years lots of people have come along and said "we want to implement shrink" and we've pointed them at the pieces that need to be put together to make it work. However, shrink is a terribly complex operation which, as Eric has pointed out, scrambles the filesystem up badly, and so for the most part it isn't a desired operation to perform on a filesystem. The reality is that nobody has needed shrink badly enough to push such a complex set of operations through to completion, or fund a developer to push it through to completion. Note that it's not just code that needs to be written, the verification of shrink behaviour and correctness is also difficult and time consuming. > I would like to continue to use XFS as it is a rock solid base since > around 10 years for us. > > But one missing piece in variable ressource usage for us is disk > shrinking. Is there any chance to get an xfs online shrinking? In a world of infinite resources at my disposal, I'd say yes. But when I already have a backlog of development work longer than my arm, finding 3-6 months to implement shrink is not easy to accomplish. And, really, reverse mapping btrees and parent pointers come first so that shrink can be implemented efficiently (shrink needs reverse block-to-path mapping), and that's another 6 months worth of work before shrink.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
