| If the hub manager goes down, you lose the management it was performing,
but the hub doesn't go down, so the network is still up and running.
It's only a failure for the management, so it's not a single point of
failure.
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| This may be tempting fate a bit, but the question deserves an answer...
The hub manager plays no part in the normal movement of traffic
through the hub; it just controls the way the modules configure
themselves when they come up (those that are configurable). For most
purposes, the hub manager could crash any time and users would not see
any effect. When the hub manager comes back up it may reconfigure the
backplane, which causes a very brief (less than a second) break in the
Ethernet flexible channels as the modules are ordered to disconnect and
reconnect. The worst effect is in token ring; as part of its self test
and initialization the hub manager has to wrap all the physical relays
that connect the token ring modules to the backplane rings. Once it is
done with initialization it will reinsert the modules, but the break
could be a few seconds (I havn't measured it).
As noted elsewhere in this conference, when the hub manager is reloaded
(yes, it is possible using DECNDU) it deletes all non-volatile
configuration information. We understand that this may cause some
distress in the field, and plan to do something less drastic for the
next release.
Note also that the hub manager can be swapped easily in the field; if
you have a customer who is concerned about such things and has enough
hubs to justify keeping a spare around they can do it themselves. the
front cover comes off by pulling the tabs on the sides inward. There
are two ribbon cables to be reconnected, but they only fit one way.
You _cannot_ do this with power on, but it doesn't take long.
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| Hello,
If the HUBmanager is not nessesary for the backplane to run, are there any
other active components in the backplane? Or is it compleatly passiv?
As I heard, for the future is planed to build the HUBmanager module
"hot-swappable", too. Is that correct? If yes, when?
Roland
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