On Mon, 7 Sep 2009, Richard Elling wrote:
Yep, it is there to try and solve the problem of rewrites in a small area, smaller than the bulk erase size. While it would be trivial to traverse the spacemap and TRIM the free blocks, it might not improve performance for COW file systems. My crystal ball says smarter flash controllers or a form of managed flash will win and obviate the need for TRIM entirely.
Without TRIM there is no way for the FLASH device to know that a region of data is free and can be reclaimed. It is pretty difficult to be intelligent without that.
Regardless, TRIM only improves the perception of performance under relatively light loads where the device is able to erase faster than the amount of writes. This is important for PCs, where perception is everything. It does not improve sustained maximum write throughput.
As far as your crystal ball goes, people here might be interested in this article about an apparent Sun product which had its documentation released to the Sun web site a bit too early:
http://www.theregister.co.uk/2009/09/03/sun_flash_array/ Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
