Red Hat nash problem

[Nifty Hat Mitch]

On Fri, Sep 10, 2004 at 12:00:08PM +0100, Paul Furness wrote:
> 
> Hmmm. It looks like it's taking its time detecting the SCSI devices. All

Detection of SCSI devices can take a long time, a very long time.

Absent devices are discovered with a timeout that can be VERY long.
This may be one of the cases where you want to disable hardware
rediscovery in the normal boot sequence once a full discovery had
taken place.

I cannot recall the timeout but I recall marveling how long it can be.
IIRC, One component of the SCSI timeout being long was the time it
takes for a SCSI tape device to power on, rewind and reply to a
command.  Many SCSI systems are set up to power each device in
sequence since +75% of the power requirements are only applicable
during spin-up/ power-on.  Instant power-up (jumper option) can require
an overly expensive PS.

If you have a handful of devices it can be fun to set the ID of each
to span the full range of possible devices so you can see blinking
lights sequence at regular intervals.  i.e. 1,2,3,4 .vs.  1,4,8,16.
Also for fun, you might watch a 1,3,4,5... sequence and time the gap
that 2 produces.

Bottom line is that devices that are healthy will be quick.  It is the
empty holes that take time.


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	T o m  M i t c h e l l 
	In the USA, be informed, Vote Nov 2004.