Storage on Floppy

[Taavi Burns]

On Tue, Apr 13, 2004 at 07:11:49AM -0400, John Wildberger wrote:
> The storage of files on floppies in Linux is different than in the "other" OS.

...not really...

> Say, you have 20 files in a directory, where each file is 400kb long. Now you 
> copy the  directory to a floppy by  " cp * /mnt/floppy" . Then you umount the 

At 20 times 400kB, you should fill the floppy after 3 files.

> floppy and subsequently mount it again. Next check what you have on the 
> floppy with "ls". It will list all the 20 files, but actually only 3 and a 

Um...that sounds like a bug.  I've never had that happen to me.

> There is no checking during storage if there is enough space left to store the 
> last  file in its entirety.

Of course there is.  Why it's not working for you is an entirely different matter...

> Also the listing of the complete directory with all the 20 files can be very 
> confusing. You might try to execute the sixth file in the list, only to get 
> an error message.

This shouldn't happen.

I can think of one possible explanation.  You start copying files, LInux starts
moving stuff over, but returns you to the command prompt early (since it does
some pretty heavy caching on async-mounted filesystems, which floppies are
normally NOT mounted as for exactly this reason).  Then you issue the unmount
command (which should not return until the cache has been flushed).  If you take
the floppy out before the cache is flushed, then yes, you'll get a corrupted
disc.  The reason that one might get Linux thinking that it has more than 1.44MB
is because (for ext2 filesystems at least) it allows one to use the disk cache as
part of the actual disk space...basically overcomitting.  Now, it should not let
you unmount in that state; it should require you to remove files until there
is enough space to cleanly unmount.

You were not very specific as to what distribution or filesystem you were using.
If you have any interest in finding out why this happened to you, it would be
helpful.

And remember: floppies are flaky!

-- 
taa

   Progress is made by lazy men looking for easier ways to do things.
      - Robert A. Heinlein
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