dan@rna.UUCP (Dan Ts'o) (05/04/88)
Has anyone had any experience with WORM (write-once optical disks) drives ? Please mail me. Since you can buy a SCSI drive for $4000 and a SCSI controller for $1500 or less, I assume a major bottleneck is the non-trivial software interface, i.e. how to make a write-once device useful. Does anyone have any thoughts as to the "proper" approach to allow "transparent" filesystem- like access, especially under UNIX ? It seems to me that a fileserver daemon could be written to emulate a UNIX filesystem and hide the inherent issues of the WORM... Cheers, Dan Ts'o 212-570-7671 Dept. Neurobiology dan@rna.rockefeller.edu Rockefeller Univ. ...cmcl2!rna!dan 1230 York Ave. rna!dan@nyu.edu NY, NY 10021 tso@rockefeller.edu
rbj@icst-cmr.arpa (Root Boy Jim) (05/05/88)
Since you can buy a SCSI drive for $4000 and a SCSI controller for $1500 or less, I assume a major bottleneck is the non-trivial software interface, i.e. how to make a write-once device useful. Does anyone have any thoughts as to the "proper" approach to allow "transparent" filesystem- like access, especially under UNIX ? It seems to me that a fileserver daemon could be written to emulate a UNIX filesystem and hide the inherent issues of the WORM... There are several approaches to WORMS. The most obvious is tape emulation, and some WORM drives actually plug into tape controllers and emulate them. Disk emulation is harder. You can either keep the index on a real disk, or write it out to create a permanent frozen read-only file system. This usually requires a specialized driver, as well as utilities to squeeze good data from one drive onto another. Yet another approach is taken by Epoch Systems in Marlborough, Mass. They gave us a presentation and told us not to say anything, so I won't say anything else except to give their phone number, which is (617) 481-3717, and to say that I was relatively impressed. They should announce soon, and will probably visit your site and give their pitch if you're interested. Cheers, Dan Ts'o 212-570-7671 Dept. Neurobiology dan@rna.rockefeller.edu Rockefeller Univ. ...cmcl2!rna!dan 1230 York Ave. rna!dan@nyu.edu NY, NY 10021 tso@rockefeller.edu (Root Boy) Jim Cottrell <rbj@icst-cmr.arpa> National Bureau of Standards Flamer's Hotline: (301) 975-5688 The opinions expressed are solely my own and do not reflect NBS policy or agreement Life is a POPULARITY CONTEST! I'm REFRESHINGLY CANDID!!
dyer@spdcc.COM (Steve Dyer) (05/06/88)
Simpson Garfinkle designed and implemented a WORM filesystem (WOFS) while
at the Media Lab at MIT. It integrates most easily into a BSD UNIX
environment through an NFS interface; he had a prototype user-mode
NFS server running on a Sun. It also looks promising for the System
5.3 file system switch. You might contact him for more details:
simsong@athena.mit.edu should suffice.
Needless to say, a properly layered SCSI driver with media-dependent
top-ends (hard disk, tape, WORM) and a controller-dependent SCSI
bottom end is also essential. If you hunt for off-the-shelf drivers,
you'll usually find that a SCSI driver will insist on treating a WORM like
a hard disk, a paradigm which is at best incomplete.
--
Steve Dyer
dyer@harvard.harvard.edu
dyer@spdcc.COM aka {ihnp4,harvard,husc6,linus,ima,bbn,m2c}!spdcc!dyer