[ http://issues.apache.org/jira/browse/HADOOP-807?page=comments#action_12456699 ] dhruba borthakur commented on HADOOP-807: -----------------------------------------
Actually, a clarification about the comment above. The DFS_CURRENT_VERSION is used by the datanode to register itself with the namenode (this is seperate from the Datanode Protocol version). This means that if we change the format of the fsimage and install a new namenode on the cluster, it cannot talk with older datanodes. Maybe this is acceptable for now. > splitting DFS version number > ---------------------------- > > Key: HADOOP-807 > URL: http://issues.apache.org/jira/browse/HADOOP-807 > Project: Hadoop > Issue Type: Bug > Components: dfs > Reporter: dhruba borthakur > Assigned To: dhruba borthakur > > In the current code, there is a enum named DFS_CURRENT_VERSION. It is being > used for three different purposes: > 1. It is stored in the fsimage and represents the format of the fsimage. > 2. It is stored in the "storage" file by the Datanodes. Thus, it represents > the format of data on Datanodes. > 3. It is used as a version of the Datanode Protocol. > The current implementation makes it difficult to change the fsimage format > without affecting the Datanode Protocol. My proposal is to introduce three > new constants, one for each of the functionality described above. > In the current code, we have: > public static final int DFS_CURRENT_VERSION = -3; > Instead, we can have: > public static final int DFS_FSIMAGE_CURRENT_VERSION = -3; > public static final int DFS_DATANODEPROTOCOL_CURRENT_VERSION = -3; > public static final int DFS_DATASTORAGE_CURRENT_VERSION = -3; > The first one is associated with the format of the fsimage/edits; the second > one is associated with the communication procotol between the namenode and > the datanode; the third one is associated with the format of the datastore on > the datanodes (e.g. directory fanout). > Please comment. -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira
