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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-18300) Implement a Multi TieredBucketCache
Date Fri, 03 Nov 2017 07:21:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18300?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16237192#comment-16237192

ramkrishna.s.vasudevan commented on HBASE-18300:

Just did some initial testing with default bucket cache with 10G offheap bucket cache and
a Tiered bucket cache with
L1 - 10 G offheap
L2 - 24 G optane SSD
L3 - 24 G fultondale SSD (PCIe SSD)
HDFS is configured to write and read from HDDs. 
I can see that with 80G data (total data set size) and with 75 threads during random reads
we get 23% improvement.  But this may not be a real time installation where people can have
the HDFS itself in PCIe SSDs. So in that case L1 and L2 cache would be ideal choice. In cloud
like deployment where there is only file based bucket cache they can allow memory based bucket
cache also to be a tier. 
As mentioned in the doc there are some TODOs and some bucket cache related clean up JIRAs
like heapspace occupancy of bucket cache etc will help here too. 

> Implement a Multi TieredBucketCache
> -----------------------------------
>                 Key: HBASE-18300
>                 URL: https://issues.apache.org/jira/browse/HBASE-18300
>             Project: HBase
>          Issue Type: New Feature
>          Components: BucketCache
>    Affects Versions: 2.0.0
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>            Priority: Major
>             Fix For: 2.1.0
> We did an internal brainstorming to study the feasibility of this. Some of our recent
tests on SSDs like Optane shows that they are vastly faster in randomreads and can act as
effective caches. 
> In the current state we have a single tier of Bucket cache and the bucket cache can either
be offheap or configured to work with file mode. (The file mode can have multiple files backing
> So this model restricts us from using either the memory or the file and not both. 
> With the advent of faster devices like Optane SSDs, NVMe based devices it is better we
try to utilize all those devices and try using them for the bucket cache so that we can avoid
the impact of slower devices where the actual data resides on the HDFS data nodes. 
> Combined with this we can allow the user to configure the caching layer per family/table
so that one can effectively make use of the caching tiers.
> Can upload a design doc here. Before that, would like to know the suggestions here. Thoughts!!!

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