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From Eli Collins <...@cloudera.com>
Subject Re: [VOTE -- Round 2] Commit hdfs-630 to 0.21?
Date Thu, 21 Jan 2010 23:22:16 GMT
+1

On Thu, Jan 21, 2010 at 2:58 PM, Tsz Wo (Nicholas), Sze
<s29752-hadoopdev@yahoo.com> wrote:
> +1
> Nicholas Sze
>
>
>
>
> ----- Original Message ----
>> From: Stack <stack@duboce.net>
>> To: hdfs-dev@hadoop.apache.org
>> Cc: HBase Dev List <hbase-dev@hadoop.apache.org>
>> Sent: Thu, January 21, 2010 2:36:25 PM
>> Subject: [VOTE -- Round 2] Commit hdfs-630 to 0.21?
>>
>> 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 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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