[plug] diagnosing dialup problems

[Brad Campbell]

Benjamin J Keith wrote:
> 5.  Try typing "hdparm -u1 -k1" at a command line prompt, be warned though
>     this may do nasty things to your drive, read the hdparm docs carefully
>     first.  My weak grasp of what this does is helps balance the speed of
>     writing of the hard drive with the speed of info coming through the
>     serial port (any elaborations??)

Close.. Sort of.
the -u1 tells the IDE driver to unmask interrupts while it is processing.
Normally the IDE driver masks ALL interruputs while it's handling one itself,
if it happens to have a holdup for some reason, it can well delay long enough
to drop chars on the serial port. This should not cause a loss of carrier, just
a resend at the ppp level. I guess in extreme cases ppp might see a stack of
bad packets in a row and hang up.

Depending on your drive/controller/motherboard/kernel -u1 may do very bad things.
Best to mount ro and do some testing first..
One test I use is to create a large file.
dd if=/dev/random of=test bs=1024 count=102400
cp test test1
then remount ro and diff the two files lots of times.
Unfortunately this does not test write integrity. I have been known to swapoff -a
mke2fs /dev/hdax (Swap device) and mount this for write, then run some write tests.

The swap partition has come in handy heaps of times I have needed a scratch disk.

-- 
Brad....
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