[Info-vax] CRTL and RMS vs SSIO

[Stephen Hoffman]

On 2021-10-07 16:18:28 +0000, Dave Froble said:

> A while back we were discussing doing away with I/O to buffers, and 
> accessing the data in place.  Slower access perhaps, but doing away 
> with the reading and writing to/from buffers.  Haven't heard much about 
> that lately.  I don't get out much.

Ayup. Nonvolatile byte-addressable storage hardware is available now, 
and is in use in various applications.

Compatible memory hardware will be rather more available for OpenVMS 
x86-64, for folks interested in investigating this for their apps.

Carving out a hunk of persistent storage will be interesting topic for 
app developers on OpenVMS, though I can think of a couple of ways to 
try.

Here's an HPE overview from a few years ago on the topic: 
https://www.pdl.cmu.edu/SDI/2016/slides/keeton-2016-10-19-memory-driven-computing.pdf 


I see some B-Tree work for this area in a newer paper, and a number of 
other discussions.

> Such type of activity would really benefit from having the capability 
> of locking just the required data, and, would need the capability of 
> reading and writing just the required data.

Locking access to the contents of a global section, or locking access 
to hardware-backed storage for external devices, is the same issue.

Whether DLM overhead is too high for that to be workable is another 
discussion that the app developers will want to ponder.

> I'm aware of how useful something like SSIO would be.  I'm just 
> appalled by the design and implementation.  As mentioned, it seems 
> aimed at just a few current uses, and totally ignores how useful it 
> would be for many more future uses.  This is rather consistent with the 
> long time apathy with which VMS has been treated.  It's more a patch 
> than an enhancement.   This is what I lament.

Alas, there's no other outcome when upward-compatibility is an 
overarching goal for the platform.



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