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From Ryan Rawson <ryano...@gmail.com>
Subject Re: [VOTE -- Round 2] Commit hdfs-630 to 0.21?
Date Thu, 21 Jan 2010 22:46:06 GMT
Scaling _down_ is a continual problem for us, and this is one of the
prime factors. It puts a bad taste in the mouth of new people who then
run away from HBase and HDFS since it is "unreliable and unstable". It
is perfectly within scope to support a cluster of about 5-6 machines
which can have an aggregate capacity of 24TB (which is a fair amount),
and people expect to start small, prove the concept/technology then
move up.

I am also +1

On Thu, Jan 21, 2010 at 2:36 PM, Stack <stack@duboce.net> wrote:
> 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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