>Shouldn't modern SSD controllers be smart enough already that they know: >- if there's a request to overwrite a sector, then the old data on >that sector is no longer needed >- allocate a "clean" sector from pool of available sectors (part of >wear-leveling mechanism) >- clear the old sector, and add it to the pool (possibly done in >background operation) > >It seems to be the case with sandforce-based SSDs. That would pretty >much let the SSD work just fine even without TRIM (like when used >under HW raid).
That is possibly not sufficient. If ZFS writes bytes to every sector, even though the pool is not full, the controller cannot know where to reclaim the data. If it uses "spare" sectors then it can map them to the to the new data and add the overwritten sectors to the free pool. With TRIM, it gets more blocks to reuse and it gives more time to erase them, making the SSD faster. Casper _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
