hadoop-hdfs-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Dhruba Borthakur <dhr...@gmail.com>
Subject Re: [VOTE -- Round 2] Commit hdfs-630 to 0.21?
Date Fri, 22 Jan 2010 18:51:22 GMT
+1 for making this patch go into 0.21.

thanks,
dhruba

On Fri, Jan 22, 2010 at 10:25 AM, Todd Lipcon <todd@cloudera.com> wrote:

> Hi Steve,
>
> All of the below may be good ideas, but I don't think they're relevant to
> the discussion at hand. Specifically, none of them can enter 0.21 without a
> vote as they'd be new features, and it doesn't even sound like there's a
> JIRA out for them yet. Let's not put off a well-known improvement patch
> waiting for one that doesn't even exist yet. If we want to get the ideas
> below into 22 or a later version, let's open a JIRA and discuss there
> rather
> than using this vote thread.
>
> As for the patch, I'm +1. It certainly is a large improvement on small
> clusters - without it, in a three node cluster, you cannot successfully
> kill
> a DN while doing an fs -put, even if your min.replication is 1. As Ryan
> mentioned above, this is a huge problem since new users may evaluate Hadoop
> on a 3-node cluster, figure "hey, let's see fault tolerance in action" and
> then be entirely put off when their kill -9 takes the cluster to a
> screeching halt.
>
> Thanks
> -Todd
>
> On Fri, Jan 22, 2010 at 7:32 AM, Steve Loughran <stevel@apache.org> wrote:
>
> > Stack wrote:
> >
> > I'm being 0 on this
> >
> > -I would worry if the exclusion list was used by the NN to do its
> > blacklisting, I'm glad to see this isn't happening. Yes, you could pick
> up
> > datanode failure faster, but you would also be vulnerable to a user doing
> a
> > DoS against the cluster by reporting every DN as failing
> >
> > -Russ Perry's work on high-speed Hadoop rendering [1] tweaked Hadoop to
> > allow the datanodes to get the entire list of nodes holding the data, and
> > allowed them to make their own decision about where to get the data from.
> > This
> >  1. pushed the policy of handling failure down to the clients, less need
> to
> > talk to the NN about it.
> >  2. lets you do something very fancy where you deliberately choose data
> > from different DNs, so that you can then pull data off the cluster at the
> > full bandwidth of every disk
> >
> > Long term, I would like to see Russ's addition go in, so worry if the
> > HDFS-630 patch would be useful long term. Maybe its a more fundamental
> > issue: where does the decision making go, into the clients or into the
> NN?
> >
> > -steve
> >
> >
> >
> > [1] http://www.hpl.hp.com/techreports/2009/HPL-2009-345.html
> >
>



-- 
Connect to me at http://www.facebook.com/dhruba

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message