EVMS team (Steve or Corry are the ones to ask i guess), Joe mentioned that you are implementing a sparse and a bbr target for device-mapper. I've got a couple of questions for you. 1. Is it read-only or read-write sparse? 1b. If it's read-write sparse it must allocate storage dynamically on writes kicking of a user space allocator waiting for those writes on a table event queue, right? 2. I assume that the bbr target uses preallocated and inaccessable table space (inaccessable in terms of regular io queued to the bbr target) to be allocated on the fly on io error? 2a. If that allocation happens, do you send an event to update metadata in user space in order to reflect the relocation? 2b. How do you guarantee that that update is atomic? 2b. Preallocation is fine to gain performance. Additionally you guys must be planning to stack bbr onto sparse (presuming read-write sparse), right? Regards, Heinz -- The LVM Guy -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Heinz Mauelshagen Sistina Software Inc. Senior Consultant/Developer Am Sonnenhang 11 56242 Marienrachdorf Germany Mauelshagen@xxxxxxxxxxx +49 2626 141200 FAX 924446 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-