The difference between multi-user thinking and single-user thinking is really quite dramatic in this area. I came up the time-sharing side (PDP-8, PDP-11, DECSYSTEM-20); TOPS-20 didn't have any sort of disk defragmenter, and nobody thought one was particularly desirable, because the normal access pattern of a busy system was spread all across the disk packs anyway.
On a desktop workstation, it makes some sense to think about loading big executable files fast -- that's something the user is sitting there waiting for, and there's often nothing else going on at that exact moment. (There *could* be significant things happening in the background, but quite often there aren't.) Similarly, loading a big "document" (single-file book manuscript, bitmap image, or whatever) happens at a point where the user has requested it and is waiting for it right then, and there's mostly nothing else going on. But on really shared disk space (either on a timesharing system, or a network file server serving a good-sized user base), the user is competing for disk activity (either bandwidth or IOPs, depending on the access pattern of the users). Generally you don't get to load your big DLL in one read -- and to the extent that you don't, it doesn't matter much how it's spread around the disk, because the head won't be in the same spot when you get your turn again. -- David Dyer-Bennet, d...@dd-b.net; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
