[Info-vax] Storage is faster than the processor

[Stephen Hoffman]

On 2016-01-07 21:18:18 +0000, David Froble said:

> ...what I got from it is that the storage would be faster than the CPU, 
> or CPUs, and now it would be the storage waiting on the CPU(s).  Or 
> possibly I got it wrong ....

Ayup.   The difficulty with present designs is that the CPUs are 
usually waiting.  Waiting for memory, seriously waiting for SSD, and 
massively waiting for HDD.

For applications with everything already in-memory, there's rather less 
of a benefit here, though faster memory is still a win.   Even for 
in-memory applications, non-volatile memory means rather less of a 
problem checkpointing the data.   Some completely different approaches 
toward that requirement become available, too.

> So, yes, making use of what used to be CPU waiting sure would speed 
> things up, but my point was, not beyond the ultimate capabilities of 
> the CPU(s).  I'm still waiting on someone smarter than me to indicate 
> how performance could go beyond that point.

By switching away from OS and application designs that have a 
traditional I/O stack and $qio calls and RMS punched-card-style 
records, for starters.

Now how the system might protect these non-volatile regions, whether 
change-mode handler or interprocess communications and selective memory 
mapping...?

> Unless you have something that is compute bound, there will always be 
> waits. For example, a business processes 10,000 orders per day.  Once 
> the 10,000 orders are processed, you're back to "nothing to do".

If the CPUs are the slow bits, then you'll usually be compute-bound.

> Regardless, faster I/O is always welcome, and perhaps VMS will need new 
> capabilities to use such speed.  Don't really know ....

Then there's that the box powers up with the OS and processes already 
in memory.    The ancient RESTART console action or recollections of 
dealing with core memory might well become meaningful again, too.

These changes are underneath HPE The Machine, too — though that project 
is going to be more than a little work for HPE.


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