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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-19357) Bucket cache no longer L2 for LRU cache
Date Wed, 06 Dec 2017 10:07:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-19357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16279947#comment-16279947
] 

Anoop Sam John commented on HBASE-19357:
----------------------------------------

We can either continue to have the HCD setter so that not just META but any user table can
set this.
Or we can internally decide when a data block comes for caching. If that belongs to a system
table, place in LRU cache. (not whole system tables may be only for META and NS also ok)..
This will be a logic  decision making with the cache block path based on table names.  
I tend to go with option #1 as the other looks hack way ..

> 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
>
>         Attachments: HBASE-19357.patch, HBASE-19357.patch, HBASE-19357_V2.patch, HBASE-19357_V3.patch,
HBASE-19357_V3.patch
>
>
> 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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