[Coco] NOS9 clusters and sectors

[Becker, Gary]

Chester

The minimum sector allocation is not the same as the cluster size. The
minimum sector allocation is the number of sectors allocated for a new
file when it is created. I guess this is to limit the fragmentation of
the drive. Since this is a multi-user OS, if NitrOS-9 did not allocate
more sectors than you needed; another user could also create a new file
while you are writing your file. And it might get allocated the next
sector on the disk before you were finished writing your file. This
would force NitrOS-9 to allocate your next sector somewhere else on the
disk causing the files to get fragmented.

Even though several sectors are allocated when the file is created,
NitrOS-9 will free any unused sectors when the file is closed.

Does this make sense and answer your question?

Gary

-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com]
On Behalf Of Chester A Patterson
Sent: Friday, August 24, 2007 2:45 PM
To: Coco @ maltedmedia.com
Subject: [Coco] NOS9 clusters and sectors

I have a 256MB CF card mounted in a Cloud9 IDE adapter as drive 0. No
other mass storage attached.
It was delivered wonderfully configured and formatted by Cloud9. No
problems whatsoever.
It is configured with HDB-DOS disk partitions 0-255 (630 sectors each)
and a 128MB OS9 /dd & /i0 partition.

So the CF card's map looks, I think, like this

Sectors	Sectors	Description
07 AC D0	502'992	CF 256MB Storage top (from IDEPROBE.BAS)
07 A3 DC	500'700	HDB-DOS Partition top (HDB offset + [630 * 256])
07 A1 66	500'070	HDB-DOS Partition 255
07 9E F0	499'440	HDB-DOS Partition 254
06 27 FA	403'050	HDB-DOS Partition 100
05 2D DC	339'420	HDB-DOS Partition 0 (HDB-DOS offset)
05 2D DB	339'419	Free area top
05 28 50	338'000	Free area top, safe
03 D0 90	250'000	Free area base, safe
03 CA 81	248'449	Free area base
03 CA 80	248'448	NOS9 Partition top (free /dd 496896 total
sectors/2)
0		0		NOS9 Partition base
0		0		CF storage base

I figure I want to claim the aprox. 40 some MB unused space (Free area
safe, in map above)
I dmode /i1 to duplicate /i0 exactly but with the following differences
cyl=157C wpc=03 ofs=D090

Accessing /i1 gives me errors 250, 251 and some others.
Also, format tells me that both /i0 and /i1 have minimum sector
allocation=8
I thought that 1 was the going number for under 128MB storage.
The descriptors /dd, /i0 and /i1 disassembled show me fcb $08 minimum
sector allocation.
Free /i0 gives me "496,896 total sectors (1-sector clusters)"

My questions are:
1. What could I be doing wrong that I can't format my /i1 40MB
partition?
2. Is it OK for format to give me minimum sector allocation=8? I tried
/1/ and got mismatch error.

Granted, I've got a LOT of space, more than I'll ever use. Wasted space
isn't really an issue. However one does tinker...

Thanks.

/Chester
Costa Rica

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