Hi Mike, Thank you for your reply. Does the thin pool can reuse the blocks that the thin-lun freed( like ssd 's discard/trim , the lun will discard the blocks to the pool ). As the filesystem creates a file (3 G bytes big, etc.) will cause the block allocation of the thin pool (thin lun), if delete the file, will the space(the blocks,3 G bytes ,etc. ) dynamically be reused now (as we think thin-lun knows the blocks delete by the FS )? or have to delete the thin-lun then the space will be reused (just thin provision only once, not support block reclamation from thin-lun to pool while lun is using )? I want to know something about the 'block (page) reclamation' before my test :) Thanks. Regards, Busby 2012/5/7, Mike Snitzer <snitzer@xxxxxxxxxx>: > On Mon, May 07 2012 at 3:28am -0400, > Busby <chaimvy@xxxxxxxxx> wrote: > >> Hi All, >> The dm-thin supports 'discard' now?Can I think this function >> likes SSD's 'TRIM'? If it just discard the block mapped but not >> remap(reallocate), the Pool's space will soon be used up . I want to >> know whether it supports block reuse ( can use ext4 with '--discard' >> test this? ) now or in the future. > > thinp discard support was added during upstream's most recent 3.4 merge > window. See: > http://git.kernel.org/linus/104655fd4dcebd500 > http://git.kernel.org/linus/67e2e2b281812b5ca > > As you can see in the commit header for this last commit, you have > control over how the discard (as issued by ext4, etc) is handled by > thinp. It should be noted that if the underlying storage does not > support discard then the thin-pool will default to no_discard_passdown > -- otherwise it does default to passing discards down to the underlying > storage. > > But you'll need 2 late fixes for thinp issues that have been found > during the 3.4-rcX development (these will be sent upstream shortly): > http://www.redhat.com/archives/dm-devel/2012-April/msg00027.html > http://www.redhat.com/archives/dm-devel/2012-April/msg00071.html > > (I'll bounce both of these patches to your email so you have them, > please apply them before building/testing the latest 3.4-rcX kernel). > > Regards, > Mike > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel