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From "Aaron T. Myers" <...@cloudera.com>
Subject Re: current direction in namenode HA
Date Tue, 04 Sep 2012 22:55:30 GMT
Hi Sujee,

On Tue, Sep 4, 2012 at 3:37 PM, Sujee Maniyam <sujee@sujee.net> wrote:

> I am trying to understand the current state / direction of  namenode
> HA implementation.

Thanks for the interest.

> For using shared directory, I see the following options
> (from
> http://www.cloudera.com/blog/2012/03/high-availability-for-the-hadoop-distributed-file-system-hdfs/
>   and  https://issues.apache.org/jira/browse/HDFS-3278)
> 1) rely on external HA filer

This is currently committed / released.

>  2) multiple edit directories

This was an option that was considered (and mentioned in the blog post you
referenced) but I don't know of anyone actively working on this.

> 3) book keeper

This is being actively developed. There's not an umbrella JIRA or label
that I'm aware of which tracks this work, but if you search the HDFS JIRA
for "bookkeeper" or "bkjm" (Bookkeeper journal manager) you should find
more info.

>  4) keep edits in HDFS / quorum based

This is also being actively developed. See this JIRA for more info:

> is there going to be an 'official / supported' method, or it is going
> to be a configurable choice when setting up a cluster?

At least for the time being, only option 1 is released. Options 3 and 4
will likely be completed / released soon, and once that happens all of
these will be mutually-exclusive options in HDFS. Each of these approaches
will coexist as a different option that can be configured when setting up
an HA HDFS cluster.

I hope that clears things up.

Aaron T. Myers
Software Engineer, Cloudera

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