[jira] Commented: (HADOOP-1762) Namenode does not need to store storageID and datanodeID persistently

["Konstantin Shvachko (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-1762?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12526648 ] 

Konstantin Shvachko commented on HADOOP-1762:
---------------------------------------------

Mostly cosmetic comments:
# Datanode.setNewStorageID():
{code}    } catch (UnknownHostException ignored) {} {code}
Should not be ignored but rather logged.
# We should  deprecate  FSEdits.OP_DATANODE_ADD and  FSEdits.OP_DATANODE_REMOVE
so that we could eventually remove them sometimes.
# FSNamesystem.registerDatanode():
{code}
        NameNode.stateChangeLog.info( "BLOCK* NameSystem.registerDatanode: "
                                      + "node " + nodeS.getName()
                                      + " is replaced by " + nodeReg.getName() +
                                      " since they have the same storageID " +
                                      nodeReg.getStorageID() +
                                      ". If this message repeats, both nodes " +
                                      "might have same storageID by random " +
                                      "chance. You need to restart one of the " +
                                      "nodes with its data cleared. ");
{code}
This message may cause confusion in the regular case.
The possibility of storage id collision is so negligible that we should not hint on it every time one node *_legally_* replaces another with the same storage id.
Let's retain the original redaction.



> Namenode does not need to store storageID and datanodeID persistently
> ---------------------------------------------------------------------
>
>                 Key: HADOOP-1762
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1762
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.14.0
>            Reporter: Raghu Angadi
>            Assignee: Raghu Angadi
>         Attachments: HADOOP-1762-Opt2.patch, HADOOP-1762-Opt2.patch, HADOOP-1762-Opt2.patch, HADOOP-1762-Opt2.patch, HADOOP-1762.patch
>
>
> Currently Namenode stores all the storage-ids it generates since the beginning (since last format). It allocates a new storageID everytime a new datanode comes online. It also stores all the known datanode ids since the beginning. 
> It would be better if Namenode did not have to keep track of these. I will describe a proposal in the next comment. 
> This has implecations regd how Namenode helps administrators identify 'dead datanodes' etc. These issues are addressed in HADOOP-1138.

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