floppy disk I/O

[Dominick Samperi]

Can somebody tell me what is a 'safe' blocking factor to use for floppy
diskette I/O, in particular, for 1.2 Meg floppies? Since these floppies
are formatted with 30 sectors per cylinder, I've been using a blocking
factor of 30, for maximum speed (I always write sequentially, starting
from the first cylinder, so this means there is minimum head movement from
one read/write to the next). Although this has worked nicely in the MS-DOS
environment, I occasionally experience data corruption when I use this
blocking factor in the UNIX environment (under both Microport's System V/AT
and SCO Xenix). Using a blocking factor of 10 seems to solve the problem,
so far...

Floppy I/O in the UNIX environment is about 4-5 times slower than it is
in the MS-DOS environment (I'm using the BIOS low-level sector read/write
calls in the MS-DOS environment). Is there a way I can give a process
exclusive access to a floppy drive in the UNIX environment, in such a
way that I can get faster and more reliable floppy I/O?

-- 
Dominick Samperi, Manhattan College, NYC
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