[OpenIndiana-discuss] Swap during install
pulaskite at yahoo.com
Tue Sep 25 22:31:38 UTC 2012
--- On Tue, 9/25/12, Richard Elling <richard.elling at richardelling.com> wrote:
> 32GB is 2 DIMMs today. It is quite easy to build a machine
> with 256GB for
> some more dollars, 1TB for a modest pile of dollars, at
> which point 2x RAM for
> swap becomes silly once again.
Which presumes several things:
That the machine will accept larger DIMMs. Mine can only take 4 GB DIMMs and is currently fully populated w/ 2 GB DIMMs. So populating to 24 GB would require replacing all the DIMMs
That there is economic justification for buying a new machine. And that there is time to acquire the machine and set it up. That is often not the case. Particularly if you just need to run a single large job
There is certainly a significant performance hit if you start paging hard. But there's great utility in being able to run an unusually large job even if it is slow. It all depends upon the software being run.
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.
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