I am on EC2, with HBase 0.94.2 and I can't find an explanation to this phenomena: I'm having these metrics on my RegionServers:
blockCacheHitRatio=87% fsReadLatencyHistogramMean= 5886103.47 fsReadLatencyHistogramMedian=6280445 fsReadLatencyHistogram75th= 28117916.5 fsReadLatencyHistogram95th= 53674180.05 Now, I am wondering, if 87% of my reads are cached, what could be the reason for 75% of the reads falling on 28.1ms - that is, I expect that the 75th percentile reads would be from cache - and with cache performance, not to mention the 95th percentile. As far as I am concerned, the mean and median are great for our use case but the tails are too wide and thick. Secondly, I've noticed that when we're running mapreduce jobs, the number of requestsPerSecond and all fs* and *requestsCount are peaking - afaik the mapper (running cascading-maple) just reads directly from HDFS and should not have any influence on the RPC's (for example) to the RegionServer and the associated metrics, what is going on with the RS metrics ? Thanks Amit
