Anoop Sam John created HBASE-19357:
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Summary: Bucket cache no longer L2 for LRU cache
Key: HBASE-19357
URL: https://issues.apache.org/jira/browse/HBASE-19357
Project: HBase
Issue Type: Sub-task
Reporter: Anoop Sam John
Assignee: Anoop Sam John
Fix For: 2.0.0-beta-1
When Bucket cache is used, by default we dont configure it as an L2 cache
alone. The default setting is combined mode ON where the data blocks to Bucket
cache and index/bloom blocks go to LRU cache. But there is a way to turn this
off and make LRU as L1 and Bucket cache as a victim handler for L1. It will be
just L2.
After the off heap read path optimization Bucket cache is no longer slower
compared to L1. We have test results on data sizes from 12 GB. The Alibaba use
case was also with 12 GB and they have observed a ~30% QPS improve over the LRU
cache.
This issue is to remove the option for combined mode = false. So when Bucket
cache is in use, data blocks will go to it only and LRU will get only index
/meta/bloom blocks. Bucket cache will no longer be configured as a victim
handler for LRU.
Note : WHen external cache is in use, there only the L1 L2 thing comes. LRU
will be L1 and external cache act as its L2. That make full sense.
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