On Tue, Jul 26, 2011 at 3:28 PM, <casper....@oracle.com> wrote: > > >>Bullshit. I just got a OCZ Vertex 3, and the first fill was 450-500MB/s. >>Second and sequent fills are at half that speed. I'm quite confident >>that it's due to the flash erase cycle that's needed, and if stuff can >>be TRIM:ed (and thus flash erased as well), speed would be regained. >>Overwriting an previously used block requires a flash erase, and if that >>can be done in the background when the timing is not critical instead of >>just before you can actually write the block you want, performance will >>increase. > > I think TRIM is needed both for flash (for speed) and for > thin provisioning; ZFS will dirty all of the volume even though only a > small part of the volume is used at any particular time. That makes ZFS > more or less unusable with thin provisioning; support for TRIM would fix > that if the underlying volume management supports TRIM. > > Casper
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). -- Fajar _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
