Date   : Thu, 30 Apr 2009 01:51:56 +0100
From   : robert@... (Rob)
Subject: Biggest Econet Fileserver Yet??

2009/4/30 Ian Wolstenholme <bbcmailinglist@...>:
>
> A problem with very large drives is the amount of space they take
> up when the file server is running - after mounting the two 512MB
> partitions, the server only had a cache of &FF7 bytes left, and
> couldn't mount a third partition due to lack of RAM (hence the
> internal error 5 in the picture earlier on). ?Whether the number of
> cylinders affects the amount of space in the file server is something
> I need to investigate more to optimise available disc space and
> server cache space.

It's probably something to do with the free space map.  The first
sector of each cylinder is used to map the used sectors on the
cylinder, one bit per sector.  So you can have an absolute maximum of
2048 sectors, 512KB, per cylinder.  So, to optimise disc space, you'd
be better using 2048/32(sectors per track) = 64 heads in the init line
you quoted.

It can't keep it all in memory all the time, as if my calculations are
right, a single 512MB drive would require a table 256KB in size, 1 bit
per sector, and you've already run a FS with two of those ..

Check the program in the disk image I linked to earlier - it reads
through the free space map; I think this version was from when I was
starting to code up the utility to actually rescue data from the
parttion.  You'd need to run it on the ARM7 CoPro to have the memory
available for that bit.

Rob