On 02/11/2015 12:25 AM, Mark Hahn wrote:
in other words: buy extra ram to hold your cold pages! after all, dram
is only O($10/GB), and disk is O($0.05/GB). oh, wait...
This comparison is overly simplistic. You're looking only at capacity
not performance, whereas this conversation is all about about
performance. If you consider the performance hit of swapping to disk,
especially in the context of HPC where performance usually overrides
cost (I said 'usually' - don't flame me!), I think just about everyone
would agree that $40 for 4 more GB of RAM is a worthwhile investment if
it has a noticeable effect on improvement.
$40 is only 2% the cost of a $2000 server. If adding that 4 GB of RAM
increases performance by more than 2%, it's worth the investment. If you
spend $0.20 on 4 GB of disk but it makes no noticeable improvement on
performance, you've wasted money, regardless of how cheap it was.
If the same comparison was applied to automobiles, we'd all be driving
school buses and Ferrari, Lamborghini and Porsche would not exist.
--
Prentice
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