Messages in this thread |  | | From | "Ulrich Windl" <> | Date | Tue, 16 Apr 1996 13:06:05 +0100 | Subject | Re: Unnecessary seeks on mounted floppies? |
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On 15 Apr 96 at 11:48, Martin Buck wrote:
> > > 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.
I thought in 1.2 the FAT filesystem driver would read-ahead larger chunks than 1.3>=59 does. This isn't perfect, but even better. I've noticed slow floppy access on minix filesystems, too (a lot of seeking). As already stated some time ago, MS-Smartdrive now reads complete tracks on the floppy; why not Linux? (The floppy controller has a read-track command, BTW)
> > Martin
Ulrich
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