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From "Chao Shi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9102) HFile block pre-loading for large sequential scan
Date Fri, 02 Aug 2013 03:01:49 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13727242#comment-13727242
] 

Chao Shi commented on HBASE-9102:
---------------------------------

bq. The client is able to enable/disable on each request basis.

Is this switch available for now? I guess this is enough to improve under our workload (as
most of our scan requests only touch 1 block). For such requests, we can enable this switch
to use pread.
                
> HFile block pre-loading for large sequential scan
> -------------------------------------------------
>
>                 Key: HBASE-9102
>                 URL: https://issues.apache.org/jira/browse/HBASE-9102
>             Project: HBase
>          Issue Type: Improvement
>    Affects Versions: 0.89-fb
>            Reporter: Liyin Tang
>            Assignee: Liyin Tang
>
> The current HBase scan model cannot take full advantage of the aggrediate disk throughput,
especially for the large sequential scan cases. And for the large sequential scan, it is easy
to predict what the next block to read in advance so that it can pre-load and decompress/decoded
these data blocks from HDFS into block cache right before the current read point. 
> Therefore, this jira is to optimized the large sequential scan performance by pre-loading
the HFile blocks into the block cache in a stream fashion so that the scan query can read
from the cache directly.

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