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From Stack <st...@duboce.net>
Subject Re: read short circuit
Date Thu, 13 Sep 2012 17:28:54 GMT
On Thu, Sep 13, 2012 at 9:51 AM, Jean-Daniel Cryans <jdcryans@apache.org> wrote:
> On Thu, Sep 13, 2012 at 9:42 AM, n keywal <nkeywal@gmail.com> wrote:
>> It's all in the "pretty much" :-)
>> Should we make it the default (i.e. recommending it in the doc, emitting a
>> warning if it's not set) for all installation ?
>
> I'd recommend it in the doc as an important config to consider.
>
> One issue with the current implementation is that you can only have 1
> user that short circuit reads, all the others who have the config
> enabled will get a fat Exception. At SU we don't have special config
> files for every MR job so unless you disable it job by job then you'll
> get those exceptions everywhere. We live with it but it did take
> people by surprise when we rolled it out :)
>
>> Or would it make sense to separate the store and wal cases, meaning that we
>> need a change in hdfs to make this possible?
>
> Don't we only have one FS instance per region server? If so, that's a
> moot point.
>

Write a short paragraph and I'll make an HDFS configuration sections
like this HBase configurations section on manual and stick it in
there: http://hbase.apache.org/book.html#perf.configurations

St.Ack

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