[ On Thursday, October 24, 2002 at 11:26:10 (-0600), Rick Kelly wrote: ]
> Subject: Re: netbsd-1-6 branch vs. recent esp(4) fixes....
>
> Greg A. Woods said:
> > 
> > (I'm also hoping the bus reset fixes will allow me to hot-swap an SCA
> > drive in an SS5/SS10/SS20 so that I can build a more reliable server
> > using RAIDframe on the root drives.  Currently doing that has dire
> > consequences for the driver just like having a drive go offline.)
> 
> Inserting or removing an internal drive from a Sun4m while it is running
> is great way to fry the system. I don't even remove or attach external
> drives to Sun systems that are powered up. I've seen too many admins in a
> hurry who killed systems that way.

Huh?  I realize the SS5/SS10/SS20 don't use SCA-II connectors but rather
just the original SCA-I variety that were not explicitly designed for
hot-swap, but that's why I need the ability to reset the bus and driver.
There's no chance of physical danger here -- only problems with data and
driver state, which is why one stops the machine first and then resets
the bus and driver and attached devices afterwards.

As for external devices, well if the bus is quiescent, and if you know
there's no problem with terminator power, and if you're careful to not
short any pins by improperly mating the connectors, then you won't cause
any damage physical.  With external devices if you always have the
device powered up when connecting or disconnecting the data cable then
you sometimes don't even glitch the bus.

I've been "hot swapping" SCSI devices on every type of machine and with
every type of connector I've ever used for well over a decade and have
never fried anything at all; not once, not ever.

(I have seen a ribbon cable cut nearly in two length-wise by someone who
didn't know better though.  They connected an incompatible device to an
old Sun-3 without checking which model it was first -- i.e. where the
system and device didn't agree on which way terminator power flowed. :-)

-- 
								Greg A. Woods

+1 416 218-0098;            <g.a.woods@ieee.org>;           <woods@robohack.ca>
Planix, Inc. <woods@planix.com>; VE3TCP; Secrets of the Weird <woods@weird.com>