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Accumulo, mail # user - 0% Data Cache Hit Rate


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0% Data Cache Hit Rate
Slater, David M. 2013-03-11, 18:48
Hi,

I have a four-node setup, and I'm running some intensive query operations that need to go through all of the rows (though only one or two column families). While I don't expect this to be fast by any means, I wanted to make sure that I had a decent baseline before comparing this to more indexed versions of querying. Here is the problem: Two of my nodes have very low data cache hit rates, wand I assume that this would greatly impact the query efficiency. Is this correct?

All four of my nodes have a 99% index cache hit rate, but the data cache hit rates are:
Node 1: 96%
Node 2: 95%
Node 3: 67%
Node 4: 0%
(All four are data nodes; the name node is #1)

I'm not seeing any warnings or errors in the logs, and I couldn't find much online about it, so I thought I would check here. Does anyone have a suggestion as for how to fix it? Could this be related to the system swappiness at all? (I currently have swappiness set to 0.)

Thanks for the help,
David Slater