Re: [9fans] fossil shutdown

["Thomas Miller" <tom@insolvencyhelp.org>]

Way back on September 22, 2005 Charles Forsyth <forsyth@terzarima.net> 
wrote:

>
> perhaps you need
>
> echo dma on >/dev/sdXX/ctl
> echo rwm on >/dev/sdXX/ctl
>

Inspired, I tried this, and I got an improvement (decrease)
in time taken to copy files to a new filename of at least
an order of magnitude.  The really interesting part of the
experiment was, however, that my computer subsequently 
failed to boot from the hard disk.  I guessed from the boot
messages that 9LOAD was not starting, and maybe the partition
0 bootloader wasn't starting.  So I booted from the install
cd and took a look at the beginning of the disk with 

cat /dev/sdC0/data | sed 10q 

I was surprised to find the letters "rwm on" right at the 
beginning of the disk.  I saved the output of 

cat /dev/sdC0/data | sed 10q > cat0.out 

at ftp.insolvencyhelp.org/pub/cat0.out if anybody wants to see. 
I decided to reinstall the partition 0 bootloader with 

disk/mbr -m /386/mbr /dev/sdC0/data

after which the machine now seems to boot just fine, and
all the files seem okay too.  For comparison, I saved the
beginning of the disk as it was *subsequent* to reinstalling
the partition 0 bootloader as cat1.out at the previously
mentioned ftp location. 

I mention all this to 9fans because I wonder whether somebody
can tell me, possibly from looking at the other differences
between the two disk images beyond just the "rwm on," what I 
did wrong.  I'm pretty sure that I did *not* type 

echo rwm on > /dev/sdC0/data     /* WRONG */

if that would cause the problem.  I have not tried to 
reproduce the problem, but I could try if people want me 
to do that.  The machine on which this occurred is an x86, 
and the disk is an IDE.  It's still running kfs. 

It certainly is nice to have multiple backups!  :-)
It certainly is nice to have Plan 9.  Thank you to Bell Labs
and 9fans. 

Kindest regards, 

Tom Miller