[OpenIndiana-discuss] Swap during install

Bob Friesenhahn bfriesen at simple.dallas.tx.us
Wed Sep 26 01:18:23 UTC 2012

On Tue, 25 Sep 2012, Reginald Beardsley wrote:
> Actually determining what makes sense requires understanding the 
> workload.  I rather doubt that 2 TB of swap space on a machine w/ 1 
> TB of DRAM would be a significant portion of the attached storage. 
> Probably not even 0.1%. The cost of even 4 TB of disk is miniscule 
> compared to the cost of 1 TB of DRAM, so I can't see any 
> justification for saying 2x is silly.  It is only silly if the 
> machine is configured so that the workload will never need to swap. 
> Not everyone has that luxury.  And people often fail to plan 
> properly to handle the workload they do have.

Your paragraph above is a perfect illustration of people failing to 
plan to properly handle the workload they do have. :-)

The fact of the matter is that most memory in modern servers is used 
for filesystem/database caching (which does not use swap) and not used 
for dirty application data pages.  Memory has become cheap enough that 
only very specialized applications will need more memory than 
available RAM.  We have reached the point where 256 GB is readily 
"affordable" without second thought for profit-making business 
purposes and even physically small systems (e.g. 1U, 2U) can be fitted 
with 1TB of RAM.

If you were to actually fill 4TB of swap with data, the program would 
likely be slow and take quite a long time to quit.  More than likely 
the program has a dreadful memory leak.

Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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