[ILUG] When servers grow up ....
kenn at bluetree.ie
Thu Aug 31 15:08:20 IST 2000
> But there is a lot to be said for a system that retains enough power to
> shutdown gracefully. It's a common feature of critical systems that you
> retain power, in a rechargeable battery or so, just enough that
> everything is left in a safe state.
VAXen took this pretty seriously. The big (i.e. non-workstation,
non-MicroVAX class) VAXen had a battery that would preserve
the contents of RAM for a while (don't know how long, but at
least minutes anyway).
Then, when booting, VMS would check if it was previously shutdown
properly or because or a power failure and, if so, was RAM still
If RAM was OK, it would pretty much continue where it left off.
Any device drivers with in-progress I/O requests would be
notified and they would do whatever was necessary to make sure
their device is back on line and re-do the request. If an
app wanted to know if a power recovery occurred, they could
register with the OS to get a notification during the later
stages or powerfail recovery.
Basically, the hardware, the OS and the drivers all co-operated
to make sure that enough state was preserved to recover
_That's_ what happens when servers grow up.
Of course, this was over 20 years ago, so I'm sure the
Intel-based world will consider it such ancient history
that there's no way they'd add features like these to their
servers and OSes. Like, VMS is _so_ passe...
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