Floppy Raid

Floppy Raid

[Stuart Inglis]

Hi all,

I've been playing with RAID over floppy (2x3.5" /dev/fd0, /dev/fd1) and
have a few questions. (With 2.4.18)

It seems clear that you can only read/write to one floppy device at a
time. Is this a hardware limit or a linux limit? fdformat to a single
drive takes around 100 seconds, whereas running two fdformats in
parallel takes close to 400 seconds (2.4.18). It looks like this is
because the lock changes when the fdformat switches from writing to
verifying.

While I have /dev/md0 setup with RAID-1 over fd0 and fd1, fdformat
/dev/fd0 fails nicely with "Device or resource busy". But I can still
mount /mnt/floppy and write to it... The changes appear on the
/mnt/floppy but not /dev/md0 until I unmount /mnt/floppy. Should this be
allowed to happen?

Cheers
Stuart

Re: Floppy Raid

[Helge Hafting]

Stuart Inglis wrote:
> 
> Hi all,
> 
> I've been playing with RAID over floppy (2x3.5" /dev/fd0, /dev/fd1) and
> have a few questions. (With 2.4.18)
> 
> It seems clear that you can only read/write to one floppy device at a
> time. Is this a hardware limit or a linux limit? fdformat to a single
> drive takes around 100 seconds, whereas running two fdformats in
> parallel takes close to 400 seconds (2.4.18). It looks like this is
> because the lock changes when the fdformat switches from writing to
> verifying.

Hardware limit _if_ you have two pc floppies on the same cable.
Use separate floppy controllers if you want simultaneous
access.  That worked fine for me back in 1992 or so.

The relieblility of floppies makes me hope you're going
for raid-1 and not raid-0...

Helge Hafting