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Varun Sharma commented on HBASE-8370: ------------------------------------- Here are some stats for this JIRA - I am arguing that the BlockCacheHit ratio number reported on a region server does not mean much. "tbl.feeds.cf.home.bt.Index.fsBlockReadCnt" : 46864, "tbl.feeds.cf.home.bt.Index.fsBlockReadCacheHitCnt" : 46864 Index Block cache hit ratio = 100 % "tbl.feeds.cf.home.bt.Data.fsBlockReadCacheHitCnt" : 202 "tbl.feeds.cf.home.bt.Data.fsBlockReadCnt" : 247 Data Block cache hit ratio = 82 % Overall Cache hit ration = (46864 + 202) / (46864 + 247) = 99 % Since Indexes are hit often, cache hits are 100 % and also # of hits is high. The real number that we are concerned about, is 82 % which is hit rate on the data block. However, we continue to show the # 99 % on the region server console instead. I think we need to fix that number. Please let me know if folks object to this ? > Report data block cache hit rates apart from aggregate cache hit rates > ---------------------------------------------------------------------- > > Key: HBASE-8370 > URL: https://issues.apache.org/jira/browse/HBASE-8370 > Project: HBase > Issue Type: Improvement > Components: metrics > Reporter: Varun Sharma > Assignee: Varun Sharma > Priority: Minor > > Attaching from mail to d...@hbase.apache.org > I am wondering whether the HBase cachingHitRatio metrics that the region > server UI shows, can get me a break down by data blocks. I always see this > number to be very high and that could be exagerated by the fact that each > lookup hits the index blocks and bloom filter blocks in the block cache > before retrieving the data block. This could be artificially bloating up the > cache hit ratio. > Assuming the above is correct, do we already have a cache hit ratio for data > blocks alone which is more obscure ? If not, my sense is that it would be > pretty valuable to add one. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira