Bob McGregor writes:

>We purchased the HP Powertrust because of it's ability to inform the 3000.
> It was a big disappointment to learn that there was no mechanism to begin
>graceful shutdown when power was interrupted.  Having a console message is
>simply not enough....

The problem is a bit more complex than this, which is probably why nobody
has seriously attacked it yet.

First, the existing "clean crash" scheme isn't as bad as it would have
been in the old days, and it is certainly an improvement over an
uncontrolled power loss. The MPE Transaction Manager insures that the
disc state is reasonably consistent, and because the halt occurs while
power is still available, there's no issue of I/O being in progress when
disc power fails. With very few exceptions (like MESSAGE FILES!!! [sorry
for shouting]), MPE and properly coded applications will recover unharmed
from the crash.

Second, there's the question of what you intend to do during any
"controlled shutdown" process. If it can't be completed within the window
of remaining power, you're no better off than you are today. So the
controlled shutdown has to start a lot earlier in the reserve window in
order to insure completion.

Then, what happens if the system is in the middle of the controlled
shutdown, and power is restored? Does your controlled-shutdown procedure
have to go all the way to shutdown and come back up, or are you going to
provide checkpoints along the way? Doing the checkpointing is quite
complex, and possibly beyond the ability of many system managers. And if
it goes all the way to shutdown and has to come back, the fact that this
will now occur more often (since it starts earlier) and take longer may
actually make the system less available overall than the "just crash"
approach.

-- Bruce


--------------------------------------------------------------------------
Bruce Toback    Tel: (602) 996-8601| My candle burns at both ends;
OPT, Inc.            (800) 858-4507| It will not last the night;
11801 N. Tatum Blvd. Ste. 142      | But ah, my foes, and oh, my friends -
Phoenix AZ 85028                   | It gives a lovely light.
btoback AT optc.com                |     -- Edna St. Vincent Millay
Mail sent to [log in to unmask] will be inspected for a
fee of US$250. Mailing to said address constitutes agreement to
pay, including collection costs.