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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-18002) Investigate why bucket cache filling up in file mode in an exisitng file is slower
Date Sat, 06 May 2017 07:47:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15999328#comment-15999328
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Anoop Sam John commented on HBASE-18002:
----------------------------------------

Seeing the code yes, there is no default location for persisting the meta data (backingMap
entries) and so the file data is not really useful when restart happens.   The issue might
be a write perf issue with the device?  For the file system, we are writing some data in certain
offsets. There might be already some data in this location (Page/block).  Our blocks might
not be aligned with the device pages also.  How it will be if the file data is cleared at
once and then write blocks? (Clear file data from code I mean)

> Investigate why bucket cache filling up in file mode in an exisitng file  is slower
> -----------------------------------------------------------------------------------
>
>                 Key: HBASE-18002
>                 URL: https://issues.apache.org/jira/browse/HBASE-18002
>             Project: HBase
>          Issue Type: Sub-task
>          Components: BucketCache
>    Affects Versions: 2.0.0
>            Reporter: ramkrishna.s.vasudevan
>             Fix For: 2.0.0
>
>
> This issue was observed when we recently did some tests with SSD based bucket cache.
Similar thing was also reported by @stack and [~danielpol] while doing some of these bucket
cache related testing.
> When we try to preload a bucket cache (in file mode) with a new file the bucket cache
fills up quite faster and there not much 'failedBlockAdditions'. But when the same bucket
cache is filled up with a preexisitng file ( that had already some entries filled up) this
time it has more 'failedBlockAdditions' and the cache does not fill up faster. Investigate
why this happens. 



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