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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2139) [hbase] Increase parallelism in region servers
Date Wed, 07 Nov 2007 00:42:51 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2139?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12540637
] 

stack commented on HADOOP-2139:
-------------------------------

Looks good. 

On 'Scans vs Cache Flush', if a flush is allowed while an outstanding scanner is running against
a 'snapshot' of hstores and some subset of memcache, for periods won't we have two copies
of data; the memory that is being flushed but which cannot be let go because it has an outstanding
scanner running against it and then the new flushed hstore on disk.

Accounting will be gnarly.  On scanner close, will have to check what of the memcache we can
let go (because its been successfully flushed).


> [hbase] Increase parallelism in region servers
> ----------------------------------------------
>
>                 Key: HADOOP-2139
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2139
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: contrib/hbase
>    Affects Versions: 0.16.0
>            Reporter: Jim Kellerman
>            Assignee: Jim Kellerman
>             Fix For: 0.16.0
>
>
> There are a number of paths in the region server which block against one another including:
> - log rolling
> - cache flushes
> - region splitting
> - updates
> - scanners
> Investigate which can proceed in parallel and mechanisms for making some operations that
currently do not run in parallel.

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