Messages in this thread | | | Date | Mon, 15 Apr 96 11:48 MET DST | Subject | Re: Unnecessary seeks on mounted floppies? | From | Martin Buck <> |
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> > to track 0 when reading from mounted floppies? > > One reason is if your floppy drive is crap or poorly aligned. The head gets > tracked back to track 0 to find out where its drifted to.
In the meantime, I've found the real reason (no, my drive is perfectly OK :-)
The DOS-fs does no read-ahead on the FAT. So whenever you read a cluster of a file that's located in a yet unread sector of the FAT, the head has to move to track 0 to read the next part of the FAT.
I added a really ugly hack that always causes the whole FAT to be read on the first access (if the FAT is small enough, i.e. on floppies). This keeps the whole FAT in the buffer cache and now I can read a complete disk without any unnecessary seeks. But this is definitely not the right solution, because other FSs (ext2, for example) seem to have similar problems.
Martin -- /* Martin Buck E-Mail: martin-2.buck@student.uni-ulm.de */ /* Student of electrical engineering WWW: http://www.uni-ulm.de/~s_mbuck1/ */ /* University of Ulm, Germany Snail-Mail: Paukengasse 2, 89077 Ulm, Germany */ #include <disclaimer.h> /* PGP Key available MIME-Mail welcome */
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