dan@SRI-TSC (04/04/83)
When I worked at Air Force Data Services Center, we came up against the same problem of trying to use archival programs to store files on multiple reels of tape. We took the general case, however, and came up with a "tool" for writing/reading multi-reel tapes. I'm suprised noone else has thought of it, since it falls right in with the UNIX concept of filters and having many small programs that do a single task each, allowing you to combine them to solve your problems. Basically, what we did was create a filter you could pipe into, which did all the dirty work of prompting for reels, watching for end of tape, writing the appropriate block size, etc. There were flags for block size, BPI, etc, as well as a -r flag to go the otherway and read from tape (and pipe the output into tar or whatever). It seems that the concept of UNIX software tools has died. Everybody is writing gargantuan programs that have a million flags and "do everything". Or even worse, taking a simple, elegant program designed to do a single task well, and hacking in a million bells and whistles so that the program does a hundred tasks, but none of them well. Unix is beginning to feel a lot like TSO... -Dan (I grew up on V6 -- a "real man's UNIX") Chernikoff dan@sri-tsc
smh (04/17/83)
Chernikoff's exposition on using a filter to handle multi-reel packing on tape backups seems pretty neat. Of course, high-volume pipes on small machines (PDP-11's) without huge buffer cache's might slow down backups somewhat, but Chernikoff neglected to mention what might be another BIG win: Tape backups on UNIX suffer because IO is synchronous. Some number of blocks of data is gathered into a buffer (typically 20 blocks) and then the backup process waits while the tape drive does its thing. Having a pipe between the disk-reading process and the tape-writing process could provide desirable IO overlaps, and could significantly increase throughput. The tape blocksize might have to be tuned to agree with pipe size. Has Dan or anyone had any experience with this? Steve Haflich MIT Experimental Music Studio ...genrad!mit-eddie!smh