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From Matt K <matvey1...@gmail.com>
Subject hbase block-cache scan.setCaching(false) not being respected
Date Mon, 02 Jun 2014 19:55:25 GMT
Hi all,

We are running a number of Map/Reduce jobs on top of HBase. We are not
using HBase for any of its realtime capabilities, only for
batch-processing. So we aren't doing lookups, just scans.

Each one of our jobs has *scan.setCaching(false)* to turn off
block-caching, since each block will only be accessed once.

We recently started using Cloudera Manager, and I’m seeing something that
doesn’t add up. See image below. It’s clear from the graphs that Block
Cache is being used currently, and blocks are being cached and evicted.

We do have *hfile.block.cache.size* set to 0.4 (default), but my
understanding is that the jobs setting scan.setCaching(false) should
override this. Since it’s set in every job, there should be no blocks being

Can anyone help me understand what we’re seeing?



[image: Inline image 1]

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