I think a picture is emerging that if you have enough RAM, the
ARC is working very well. Which means that the ARC management
is suspect.
I propose the hypothesis that ARC misses are not prefetched. The
first time through, prefetching works. For the second pass, ARC
misses are not prefetched, so sequential reads go slower.
For JBODs, the effect will be worse than for LUNs on a storage array
with lots of cache. benr's prefetch script will help shed light on this,
but apparently doesn't work for Solaris 10. Since the Solaris 10
source is not publicly available, someone with source access might
need to adjust it to match the Solaris 10 source.
-- richard
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