[gPXE] Fw: Fw: Booting MS-DOS using gPXE/iSCSI: C: drive is readonly

[Jonathan Andrews]

> 
> Note that the FAT filesystem (like so many other filesystems) is not 
> intended for simultaneous use by multiple clients; that would be like 
> having a hard drive physically attached to multiple computers with a 
> spider-web of IDE ribbons spliced together and expecting the OS
running 
> on each computer to magically co-operate when writing to the
filesystem 
> without any awareness of the other OSs.  I'm not suggesting that
you're 
> doing this.

Just as a point of interest I did once do *almost* this.  I was the
proud owner of an ISA MFM drive multiplex card that would split one
drive between two ISA hosts.  It did sort of work, mostly because early
DOS does not buffer the directory entries, each access was in effect a
serial read before write, so two hosts creating a file on FAT filesystem
works, each one gets the next free cluster, as read is blocking and
syncro this mostly works.  What does not work is writing random blocks
without locking from two hosts within the same file - so any database
type application would tend to corrupt the disk... as did parallel
renames etc. The device was intended for a small "common" read only fat
partition and one active partition per host. The product died when drive
prices dropped, remember at the same point in the timeline an ISA
Ethernet card was $800 and Novell was the only game around.

Cheers,
Jon