RAD_SUPPORT on non-Galaxy GS1280s?

[Ken F.]

I've inherited a 4-node VMScluster consisting of
a pair of GS1280's hard-partitioned into 2 nodes
each, running VMS 7.3-2. We are not running in a
Galaxy configuration and don't have a Galaxy
license loaded. We're no more than 6 months out
of date on ECOs.

In going through a series of Autogen's in
preparation for a cluster reboot this weekend,
I discovered that the SYSGEN parameter
RAD_SUPPORT changed from 0 (zero) to 207
(%x00CF). Having not previously encountered
this parameter before, I reviewed the Help
Sys_Parameters for RAD_SUPPORT, and would like
to know a couple of things:

1) The Help entry says a value of 79 is the
default, but SYSGEN shows the default as
207, which is basically setting bit 7,
marked as reserved to HP. Does anyone
know why this would be a problem?

2) More importantly, what is the effect of
a non-zero RAD_SUPPORT on systems that aren't
configured as a Galaxy? In particular, is it
a "bad" thing to have this set to the SYSGEN
default? Do we stand to gain in performance
with the default?

Any advise or insights would be most welcome!

Thanks, Ken

[EdgarZamora]

207 is the default. The help message probably needs updating.

IMO, RADs are only meaningful on Wildfire systems and not on the modern GS1280s. I would leave the parameter alone and not worry about it.

[John Gillings · Accepted solution]

Ken,

RADs and Galaxy are independent.

RADs are used to try to keep processes close to data in systems where access to different areas of memory is non uniform (NUMA = Non Uniform Memory Access). The idea is to try and keep a process within a single RAD (Resource Affinity Domain? = a group of processors and memory), to optimise memory access.

Galaxy is a kind of soft partitioning. It only relates to RADs in that the partitions should take them into account, so, for example, one partition isn't accessing memory in a RAD on another partition.

RADs were important on the older EV6 "Wildfire" systems which had some fairly serious skew in NUMA. GS1280s are EV7s which exhibit far more uniform memory access (though not completely uniform). For most applications the performance difference with RADs enabled or disabled is negligible.

[Ken F.]

Thanks Edgar and John, I'll leave it set to
its default value.

I was unaware that one didn't need to worry
as much about RADs with the GS1280's as with
the old Wildfires. And as I said, I've
inherited these systems and have never seen
their "insides" nor talked with HP field
service about the physical configuration, so
I've been especially careful with the changes
I'm making.

-Ken

[Ken F.]

I'll leave RAD_SUPPORT at its default value and not worry about it. :-)