On 6/19/12 9:19 AM, Ted Ts'o wrote: > On Tue, Jun 19, 2012 at 04:09:48PM +0200, Lukáš Czerner wrote: >> >> With thin provisioning you'll get totally different file system >> layout than on fully provisioned disk as you push more and more >> writes to your drive. This unfortunately has great impact on >> performance since file systems usually have a lot of optimization on >> where to put data/metadata on the drive and how to read them. >> However in case of thinly provisioned storage those optimization >> would not help. And yes, you just have to expect lower performance >> with dm-thin from the file system on top of it. It is not and it >> will never be ideal solution for workloads where you expect the best >> performance. > > One of the things which would be nice to be able to easily set up is a > configuration where we get the benefits of thin provisioning with > respect to snapshost, but where the underlying block device used by > the file system is contiguous. That is, it would be really useful to > *not* use thin provisioning for the underlying file system, but to use > thin provisioned snapshots. That way we only pay the thinp > performance penalty for the snapshots, and not for normal file system > operations. This is something that would be very useful both for ext4 > and xfs. I agree, and have asked for exactly the same thing... though I have no idea how hard it is to disentangle allocation-aware snapshots from thing provisioned storage. -Eric -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
