Hello there, Hitachi USP-V (sold as 9990V by Sun) provides thin provisioning, known as Hitachi Dynamic Provisioning (HDP). This gives a way to make the OS believes that a huge lun is available whilst its size is not physically allocated on the DataSystem side. A simple example : 100Gb seen by the OS but only 50Gb physically allocated in the frame, in a physical devices stock (called a HDP-pool) The USP-V is now able to reclaim zero pages that are not used by a Filesystem. Then, it could put them back to this physical pool, as free many 42Mb blocks. As far as I know, when a file is deleted, zfs just stop to reference blocks associated to this file, like MMU does with RAM. Blocks are not deleted, nor zeored (sounds very good to get back to some files after a crash !). Is there a way to transform - a posteriori or a priori - these "unreferenced blocks" to "zero blocks" to make the HDS-Frame able to reclaime these ones ? I know that this will create some overhead... It might leads to a smaller "block allocation history" but could be very usefull for zero-pages-reclaim. I do hope that my question was clear enough... Thanx for your hints, Cyril Payet
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