On Wed, 6 May 2026 19:05:06 +0000, Glen Garrison <[email protected]> wrote:

>I have not specifically looked at what the general population have specified 
>for RSU.
>   But I do know that many systems out there have initial and reserved 
> specified and have seen where some set rsu equal to their reserved, so some 
> must be config'ing that offline for use by other lpars.  Generally 
> RSU=OFFLINE.   I have also seen RSU=0 with reserved defined.

I always liked RSU=OFFLINE on the theory that if we needed that reserved 
storage for dealing with an unexpected demand for memory, then we could (in 
theory) take it back offline so some other LPAR could use it. However it never 
seemed to work out quite that simply. And that was back in the day when systems 
when memory sizes were generally much smaller. 

Today, at least on the big machines, it seems most customers are less 
constrained, in part because the minimum orderable config is 512GB. That's not 
so true on the smaller (e.g. "BC") machines where the minimum orderable memory 
remains stuck at 64GB and some systems that really could benefit from more 
memory nonetheless end up not getting it during system refreshes, presumably 
due to cost concerns. But possibly also because they're only considering their 
non-existent paging as a lack of demand for memory and not investigating how 
much I/O they could avoid if they had more memory. 

Scott Chapman

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