d757@sphinx.UChicago.edu (Lawrence Lerner) (10/19/87)
[ Hey, Fred, perhaps you can say something about optical disks... -DL ]
You want an opinion? Ok, how is the current research going to incorporate
the advances in hardware. Specifically optical disks? I attended a seminar
sometime ago on the use of optical disks. Apparently it is possible
to store many a megabyte on very little space, ok no biggie it's been
available for a while (yes it's not eraseable, well that's hardware) but
I was under the impression that the retrieval time is something slightly
less than phenomonal. Are OS being designed to take advantage of this
vastly expanded memory and data call up time?
As an undergrad with a few CS courses under my belt what are some good
books or reports to read for new developments in OS????
[ Almost never books. If you want something new, really new, then the ]
[ place to look is in conference proceedings. It takes at least one ]
[ year for anything to make it into journals. ]
"Never ask me to ask a question"
-He who asks uncomforatble questions.--
"...nothing kills that does not know ye."
"The Elf Glade"
UUCP: ihnp4!gargoyle!sphinx!d757 d757@sphinx.uchicago.edu
Lawrence Lerner University of Chicago Computation Center douglis@sloth.Berkeley.EDU (Fred Douglis) (10/20/87)
I'd like to respond to Lawrence Lerner's note about optical disks. I'm a grad student at U.C. Berkeley working on the Sprite project; I am currently starting research on the use of optical disks for archiving and file migration. There are a number of write-once optical disks already available on the market, and write-many disks will be available in the next few years. I have had some experience with the Maxtor 800S drive: 400MB/side, double-sided, SCSI-based. Last summer at DEC WRL, I implemented a primitive archive service using the Maxtor drive -- we measured transfer rates on the order of 30KB/sec writing and 70KB/sec reading, with no measurements of the latency at the time I left. I believe that the 12" drives have much better transfer rates than the 5 1/4" drives; also, the device driver was not at all optimized, so the rates I measured were pessimistic. Still, there's a big difference between the performance of a magnetic disk and that of an optical disk, just like there's a big difference between memory and magnetic disks. Treat the optical disks like another level in the cache hierarchy, and everything's just fine. We asked ourselves what one could do with vast amounts of write-once storage, and we decided to try to use optical disks to store old versions of files, so that people could turn the clock back to see the file system as of an earlier point in time. The same mechanism could be used to remove unused files from magnetic disks and restore them (in a "short" time) from optical disks if they are later referenced. Large memories and magnetic disk caches would be used to keep the I/O to the optical disk to a minimum. A number of issues come up with respect to automatic archival of old files. We have to decide how to deal with log files (we wouldn't want to rewrite several megabytes every time a few bytes are appended), and we have to perform measurements to decide if it's feasible to store all versions of all files or to exclude large, recreatable files such as executables. The file system would probably have to be modified to tag files with attributes (temporary, append-only, etc.). We must decide on data structures to facilitate efficient access to old versions of files: given a time, what version of each file (if any) existed at that point? The research I'd like to do is pretty preliminary at this point, and I'd welcome feedback from anyone who would like to comment. Right now, I'm reviewing previous work in the area (e.g., Swallow (MIT), and file migration work at the University of Illinois). I'd appreciate any pointers to other relevant work, or any other suggestions. Please direct them to: douglis@ginger.Berkeley.EDU ...!ucbvax!douglis - Fred - - Fred -
lmcvoy@eta.eta.com (Larry McVoy) (10/21/87)
In article <4130@sdcsvax.UCSD.EDU> d757@sphinx.UChicago.edu (Lawrence Lerner) writes: > As an undergrad with a few CS courses under my belt what are some good >books or reports to read for new developments in OS???? I'd say that the following are required reading: Peterson & Silberschatz, Edition II (very nice for general OS concepts, summarizes the "good" ideas in that have come out of both research & practice). CS 736 reading list: or your approximation. Go buy the papers for a grad level course on OS, preferable from a hot OS school (know anyone at CMU? UCB?). Most of the stuff is in P&S but if the prof is on the ball [s]he'll have added the newest & greatest. Doug Comer's Xinu books (both are great). Bach's book on UNIX if you really want to know. (Skip the Lyons doc, it's too out of date). The AT&T tech journals on unix: basic, basic, basic. The MACH papers from CMU - just ask and they shalt deliver. The Sprite papers from Berkeley. OK, all done? Now you're ready to start looking at slightly old stuff :-) A good place to start is a workstation with unix src (doesn't really matter which version, they all have run queues...) Poke around a bit. Write a device driver that uses a different strategy... See how it works now. This will take more than ten minutes (unless you're above average :-) OK. Now start reading journals. Going straight to the journals is probably a mistake - you don't appreciate it yet. Enjoy, enjoy, -- Larry McVoy uucp: ...!{uiucuxc, rosevax, meccts, ihnp4!laidbak}!eta!lmcvoy arpa: eta!lmcvoy@uxc.cso.uiuc.edu or lm@arizona.edu