Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rochester!cornell!batcomputer!braner From: braner@batcomputer.tn.cornell.edu (braner) Newsgroups: comp.sys.atari.st Subject: Re: Re: A challenge to you disk experts Message-ID: <1911@batcomputer.tn.cornell.edu> Date: Tue, 23-Dec-86 23:06:36 EST Article-I.D.: batcompu.1911 Posted: Tue Dec 23 23:06:36 1986 Date-Received: Wed, 24-Dec-86 05:37:50 EST References: <1895@batcomputer.tn.cornell.edu> <496@atari.UUcp> Reply-To: braner@batcomputer.UUCP (braner) Organization: Theory Center, Cornell University, Ithaca NY Lines: 37 Summary: A cache for floppy use IS possible and DESIRED! [] Thanks to Allan for the expert advice. My goal is not to minimize disk head movement, but to minimize disk use. Period. Unnecessary head movement causes longer disk-turning periods --> more disk (and head) wear (and more waiting time). I used a 27K buffer for disk read in AUTOCOPY since the speed does not increase significantly for larger buffers. (Indeed, the speed is almost up to its max with 9K!) There I used Fread() to read into the buffer. In AUTODISK (recently posted) I used Rwabs(), as Allen suggested. The whole idea behind AUTODISK is that I copy the whole disk as a block, starting with reading the boot sector and FAT, so I know how much to read on without re-reading anything. I very much wish I had a good disk-cache program. That would eliminate not only the need for dirty tricks like AUTODISK, but also (with a BIG cache) the need for a RAMdisk! The problem of handling disk-swappings (by the user, with no warning) is serious, but not insurmountable. For example, one could write a cache program that would keep track of the disk things came off of (not just sectors and drives), and would NOT delay WRITING of data to the physical disk. The former feature would allow handling data from two or more disks with one drive and no extra swapping, and the latter would avoid writing on the wrong disk and also after-the-fact reporting of write errors (common on floppies...). If the user does not swap disks too often, the program would not need to check the disk ID very often, and GREAT increases in disk throughput would become possible!! If I had the time for a large project like that, a GOOD disk-cache program would be my very first choice! Anybody out there up to it? Of course I've spent time on AUTOCOPY and AUTODISK, perhaps more than I'd ever regain from them. But EVERYBODY can now use them for free! It's part of my share in the great world of Public Domain Software. - Moshe Braner