So while I'm feeling optimistic :-) we really ought to be able to do this in two I/O operations. If we have, say, 500K of data to write (including all of the metadata), we should be able to allocate a contiguous 500K block on disk and write that with a single operation. Then we update the überblock.
The only inherent problem preventing this right now is that we don't have general scatter/gather at the driver level (ugh). This is a bug that should be fixed, IMO. Then ZFS just needs to delay choosing physical block locations until they’re being written as part of a group. (Of course, as NetApp points out in their WAFL papers, the goal of optimizing writes can conflict with the goal of optimizing reads, so taken to an extreme, this optimization isn’t always desirable.) This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
