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From Stack <st...@duboce.net>
Subject [VOTE -- Round 2] Commit hdfs-630 to 0.21?
Date Thu, 21 Jan 2010 22:36:25 GMT
I'd like to propose a new vote on having hdfs-630 committed to 0.21.
The first vote on this topic, initiated 12/14/2009, was sunk by Tsz Wo
(Nicholas), Sze suggested improvements. Those suggestions have since
been folded into a new version of the hdfs-630 patch.  Its this new
version of the patch -- 0001-Fix-HDFS-630-0.21-svn-2.patch -- that I'd
like us to vote on. For background on why we -- the hbase community
-- think hdfs-630 important, see the notes below from the original
call-to-vote.

I'm obviously +1.

Thanks for you consideration,
St.Ack

P.S. Regards TRUNK, after chatting with Nicholas, TRUNK was cleaned of
the previous versions of hdfs-630 and we'll likely apply
0001-Fix-HDFS-630-trunk-svn-4.patch, a version of
0001-Fix-HDFS-630-0.21-svn-2.patch that works for TRUNK that includes
the Nicholas suggestions.


On Mon, Dec 14, 2009 at 9:56 PM, stack <stack@duboce.net> wrote:
> I'd like to propose a vote on having hdfs-630 committed to 0.21 (Its already
> been committed to TRUNK).
>
> hdfs-630 adds having the dfsclient pass the namenode the name of datanodes
> its determined dead because it got a failed connection when it tried to
> contact it, etc.  This is useful in the interval between datanode dying and
> namenode timing out its lease.  Without this fix, the namenode can often
> give out the dead datanode as a host for a block.  If the cluster is small,
> less than 5 or 6 nodes, then its very likely namenode will give out the dead
> datanode as a block host.
>
> Small clusters are common in hbase, especially when folks are starting out
> or evaluating hbase.  They'll start with three or four nodes carrying both
> datanodes+hbase regionservers.  They'll experiment killing one of the slaves
> -- datanodes and regionserver -- and watch what happens.  What follows is a
> struggling dfsclient trying to create replicas where one of the datanodes
> passed us by the namenode is dead.   DFSClient will fail and then go back to
> the namenode again, etc. (See
> https://issues.apache.org/jira/browse/HBASE-1876 for more detailed
> blow-by-blow).  HBase operation will be held up during this time and
> eventually a regionserver will shut itself down to protect itself against
> dataloss if we can't successfully write HDFS.
>
> Thanks all,
> St.Ack

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