On Tue, Jun 19 2012 at 10:43am -0400, Alasdair G Kergon <agk@xxxxxxxxxx> wrote: > On Tue, Jun 19, 2012 at 10:19:33AM -0400, Ted Ts'o wrote: > > 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. > > We're tracking this requirement (for lvm2) here: > https://bugzilla.redhat.com/show_bug.cgi?id=814737 That is an lvm2 BZ but there is further kernel work needed. It should be noted that the "external origin" feature was added to the thinp target with this commit: http://git.kernel.org/linus/2dd9c257fbc243aa76ee6d It is start, but external origin is kept read-only and any writes trigger allocation of new blocks within the thin-pool. We've talked some about the desire to have a fully provisioned volume that only starts to get fragmented once snapshots are taken. The idea is to move the origin into the data volume, via mapping, rather than copying: Dec 14 10:37:08 <ejt> we then build a data dev that consists of a linear mapping to that origin Dec 14 10:37:12 <ejt> plus some extra stuff Dec 14 10:37:23 <ejt> (the additonal free space for snapshots) Dec 14 10:37:49 <ejt> we then prepare thinp metadata with a mapping to that origin -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
