We have an awesome community resource in our online book. It's maintained and looked after with
diligence. We also have an HBase section on the hadoop wiki that hasn't been updated since 2012.
Let's sift through the pages of the wiki, bring over any content that's still relevant and
not already present in the book, and kill the wiki.
In HBASE-8370 "Report data block cache hit rates apart from aggregate cache hit rates"
discussion highlights small changes in caching percentage can make for large
changes in cache contents; e.g. lots of data blocks may be getting evicited
but because meta blocks -- index and blooms -- are staying in cache with
high hit rates, a large data block eviction may show as a small change in
overall cache percentage (e.g. from 99.99 to 99.11).
Changes the getBlockCacheHitPercent from an int to a double.
Also changes name of the jmx metric blockCountHitPercent to be
blockCacheCountHitPercent instead.
May be incompatible change.
