Juergen Nickelsen <n...@jnickelsen.de> wrote: > joerg.schill...@fokus.fraunhofer.de (Joerg Schilling) writes: > > > The netapps patents contain claims on ideas that I invented for my Diploma > > thesis work between 1989 and 1991, so the netapps patents only describe > > prior > > art. The new ideas introduced with "wofs" include the ideas on how to use > > COW > > for filesystems and on how to find the most recent "superblock" on a COW > > filesystem. The ieas for the latter method have been developed while > > discussing the "wofs" structure with Casten Bormann at TU-Berlin. > > Would you perhaps be willing to share the text? Sounds quite > interesting, especially to compare it with ZFS and with Netapp's > introduction to WAFL that I read a while ago.
If you are interested in the text, this is here: http://cdrecord.berlios.de/private/wofs.ps.gz (this is the old original without images as they have not been created with troff) http://cdrecord.berlios.de/private/WoFS.pdf (this is a reformatted version with images included). If you like to see the program code, I am considering to make it available at some time. > (And I know that discussions with Carsten Bormann can > result in remarkable results -- not that I would want to disregard > your own part in these ideas. :-) Yes, he is a really helpful discussion partner. As a note: the basic ideas for implementing COW (such as inverting the tree structure in order to avoid to rewrite all directories upwards to the root directory in case that a nested file is updated, the idea to use generation nodes called "G-nodes" and the idea on how updated super blocks can be found) have been invented by me. Carsten helped to develop a method that allows to define and locate extension areas for updated super blocks for the case when the primary super clock update area has become full. The latter idea is not needed on a hard disk based filesystem as hard disks allw to overwrite old superblock locations. On a WORM media, this is essential to make sure that the medium is usable for writing as long as there are unwritten blockd. Jörg -- EMail:jo...@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin j...@cs.tu-berlin.de (uni) joerg.schill...@fokus.fraunhofer.de (work) Blog: http://schily.blogspot.com/ URL: http://cdrecord.berlios.de/private/ ftp://ftp.berlios.de/pub/schily _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
