bsousa wrote:
> ARC Size Breakdown:
>          Most Recently Used Cache Size:          88%    4078 MB (p)
>          Most Frequently Used Cache Size:        11%    550 MB (c-p)
>
>   

Okey, so 88% of the ARC contents have only been hit once, and 11% are
being hit over and over. 

> So now i'm even more confused...in the ARC Efficency we see :
>
> Data Demand   Efficiency:    52%
> Data Prefetch Efficiency:    58%
>
> is this a good thig or a bad thing?
>   


This is actually good.  It means that 52% of the cache hits are blocks
your asking for again, and 58% are blocks you've never asked for but
were prefetched ahead of time.

On a lot of server systems you'll see prefetch efficiency really low...
like 10% or lower.  In those cases the additional I/O may not be worth
it, however in your case 58% of the cache hits are prefetched bits that
you don't need to do I/O to disk for...which is kool.

So I'd recommend leaving prefetch alone. :)

benr.
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