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Hadoop QA commented on HDFS-4257: --------------------------------- {color:green}+1 overall{color}. Here are the results of testing the latest attachment http://issues.apache.org/jira/secure/attachment/12662703/h4257_20140819.patch against trunk revision . {color:green}+1 @author{color}. The patch does not contain any @author tags. {color:green}+1 tests included{color}. The patch appears to include 1 new or modified test files. {color:green}+1 javac{color}. The applied patch does not increase the total number of javac compiler warnings. {color:green}+1 javadoc{color}. There were no new javadoc warning messages. {color:green}+1 eclipse:eclipse{color}. The patch built with eclipse:eclipse. {color:green}+1 findbugs{color}. The patch does not introduce any new Findbugs (version 2.0.3) warnings. {color:green}+1 release audit{color}. The applied patch does not increase the total number of release audit warnings. {color:green}+1 core tests{color}. The patch passed unit tests in hadoop-hdfs-project/hadoop-hdfs. {color:green}+1 contrib tests{color}. The patch passed contrib unit tests. Test results: https://builds.apache.org/job/PreCommit-HDFS-Build/7681//testReport/ Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/7681//console This message is automatically generated. > The ReplaceDatanodeOnFailure policies could have a forgiving option > ------------------------------------------------------------------- > > Key: HDFS-4257 > URL: https://issues.apache.org/jira/browse/HDFS-4257 > Project: Hadoop HDFS > Issue Type: New Feature > Components: hdfs-client > Affects Versions: 2.0.2-alpha > Reporter: Harsh J > Assignee: Tsz Wo Nicholas Sze > Priority: Minor > Attachments: h4257_20140325.patch, h4257_20140325b.patch, > h4257_20140326.patch, h4257_20140819.patch > > > Similar question has previously come over HDFS-3091 and friends, but the > essential problem is: "Why can't I write to my cluster of 3 nodes, when I > just have 1 node available at a point in time.". > The policies cover the 4 options, with {{Default}} being default: > {{Disable}} -> Disables the whole replacement concept by throwing out an > error (at the server) or acts as {{Never}} at the client. > {{Never}} -> Never replaces a DN upon pipeline failures (not too desirable in > many cases). > {{Default}} -> Replace based on a few conditions, but whose minimum never > touches 1. We always fail if only one DN remains and none others can be added. > {{Always}} -> Replace no matter what. Fail if can't replace. > Would it not make sense to have an option similar to Always/Default, where > despite _trying_, if it isn't possible to have > 1 DN in the pipeline, do not > fail. I think that is what the former write behavior was, and what fit with > the minimum replication factor allowed value. > Why is it grossly wrong to pass a write from a client for a block with just 1 > remaining replica in the pipeline (the minimum of 1 grows with the > replication factor demanded from the write), when replication is taken care > of immediately afterwards? How often have we seen missing blocks arise out of > allowing this + facing a big rack(s) failure or so? -- This message was sent by Atlassian JIRA (v6.2#6252)