On Sat, 18 Apr 2009, Eric D. Mudama wrote:
What is tall about the SATA stack? There's not THAT much overhead in SATA, and there's no reason you would need to support any legacy transfer modes or commands you weren't interested in.
If SATA is much more than a memcpy() then it is excessive overhead for a memory-oriented device. In fact, since the "device" is actually comprised of quite a few independent memory modules, it should be possible to schedule I/O for each independent memory module in parallel. A large storage system will be comprised of tens, hundreds or even thousands of independent memory modules so it does not make sense to serialize access via legacy protocols. The larger the storage device, the more it suffers from a serial protocol.
Many years ago Sun implemented memory mapped files with copy-on-write semantics. Unfortunately, this was still tied to a legacy block device. It is time to think more in parallel and prepare for the future.
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
