Re: High Availability PC Based Home Automation

[Jamie Whitehorn <jamie@xxxxxxxxxxxxxxx>]

Hi Rob,

You didn't say what HA system it is, but there's hints in your message that
it's already been chosen. If it hasn't been finalised you might want to
have a look at Idratek (www.idratek.com) as a lot of what you are looking
for has already been builtin to the system from the ground up.

Idratek works by having a series of intelligent modules connected by CAT5
cable running an RS432 protocol. The controlling software, Cortex, is run
on a standard Windows PC, and talks to the Idratek modules using the
standard R232 interface. As part of the Cortex install a separate monitor
program is installed which can automatically re-start Cortex if it fails on
that PC. But now the magic start, as the guys at Idratek have obviously
thought about this alot  ...

The Idratek modules are rightly called intelligent and have the ability to
initiate actions independently and communicate amongst themselves. So for
example a sensor on the ground floor can be setup to turn on a light
upstairs; an IR receiver can learn a number of codes and send different
messages to other modules depending on the code it receives. The magic here
is this is all independent of the PC and Cortex. It's a system known
Reflex. The analogy being to how your body works, simple things are done by
reflex, complex actions are done by your brain (Cortex). The reflex actions
are fully programmable and are setup by the user/installer.

In normal operation the system runs using Cortex, in the event that the
Cortex PC or program fails, the Idratek system can be setup to revert to
Reflex operation automatically. This is done by a series of watchdog timers
running in certain modules, in the event that any of them detect a failure
of the Cortex PC, they'll switch the system to Reflex. It can also be done
manually if you want to do maintenance on the PC.

But you can go further still. You can install an additional copy of Cortex
on a separate PC (additional licence required), that is set to monitor the
first copy and only activate if the first copy goes off line for what ever
reason. This gives you the resilience against PC failure, blue screen, etc
without having to go to extremes of Windows Clustering (which is not for
the faint of heart by the way, so unless your customer is very, very
computer literate I really wouldn't go there).

However if you really do need to go down the HA route for a Windows PC /
Server, contact me off list and we can have a chat on the phone. Sad to say
I have done an awful lot of these for my day job. However, generally
speaking, to do it properly is not simple and is not cheap.

Usual disclaimer - I don't work for Idratek or have any connection with
them other than being a happy customer who keeps buying lots of nice
hardware from them.

HTH, Jamie






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