[jira] [Commented] (HBASE-7404) Bucket Cache:A solution about CMS,Heap Fragment and Big Cache on HBASE

["Jonathan Hsieh (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-7404?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13730126#comment-13730126 ] 

Jonathan Hsieh commented on HBASE-7404:
---------------------------------------

I've filed HBASE-9131 -- it would be great if someone who worked on this code added documentation at an admin-level to the ref guide.
                
> Bucket Cache:A solution about CMS,Heap Fragment and Big Cache on HBASE
> ----------------------------------------------------------------------
>
>                 Key: HBASE-7404
>                 URL: https://issues.apache.org/jira/browse/HBASE-7404
>             Project: HBase
>          Issue Type: New Feature
>    Affects Versions: 0.94.3
>            Reporter: chunhui shen
>            Assignee: chunhui shen
>             Fix For: 0.95.0
>
>         Attachments: 7404-trunk-v10.patch, 7404-trunk-v11.patch, 7404-trunk-v12.patch, 7404-trunk-v13.patch, 7404-trunk-v13.txt, 7404-trunk-v14.patch, BucketCache.pdf, hbase-7404-94v2.patch, HBASE-7404-backport-0.94.patch, hbase-7404-trunkv2.patch, hbase-7404-trunkv9.patch, Introduction of Bucket Cache.pdf
>
>
> First, thanks @neil from Fusion-IO share the source code.
> Usage:
> 1.Use bucket cache as main memory cache, configured as the following:
> –"hbase.bucketcache.ioengine" "heap"
> –"hbase.bucketcache.size" 0.4 (size for bucket cache, 0.4 is a percentage of max heap size)
> 2.Use bucket cache as a secondary cache, configured as the following:
> –"hbase.bucketcache.ioengine" "file:/disk1/hbase/cache.data"(The file path where to store the block data)
> –"hbase.bucketcache.size" 1024 (size for bucket cache, unit is MB, so 1024 means 1GB)
> –"hbase.bucketcache.combinedcache.enabled" false (default value being true)
> See more configurations from org.apache.hadoop.hbase.io.hfile.CacheConfig and org.apache.hadoop.hbase.io.hfile.bucket.BucketCache
> What's Bucket Cache? 
> It could greatly decrease CMS and heap fragment by GC
> It support a large cache space for High Read Performance by using high speed disk like Fusion-io
> 1.An implementation of block cache like LruBlockCache
> 2.Self manage blocks' storage position through Bucket Allocator
> 3.The cached blocks could be stored in the memory or file system
> 4.Bucket Cache could be used as a mainly block cache(see CombinedBlockCache), combined with LruBlockCache to decrease CMS and fragment by GC.
> 5.BucketCache also could be used as a secondary cache(e.g. using Fusionio to store block) to enlarge cache space
> How about SlabCache?
> We have studied and test SlabCache first, but the result is bad, because:
> 1.SlabCache use SingleSizeCache, its use ratio of memory is low because kinds of block size, especially using DataBlockEncoding
> 2.SlabCache is uesd in DoubleBlockCache, block is cached both in SlabCache and LruBlockCache, put the block to LruBlockCache again if hit in SlabCache , it causes CMS and heap fragment don't get any better
> 3.Direct heap performance is not good as heap, and maybe cause OOM, so we recommend using "heap" engine 
> See more in the attachment and in the patch

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