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 <ste...@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 >
