[ http://issues.apache.org/jira/browse/HADOOP-807?page=comments#action_12457011 ] Konstantin Shvachko commented on HADOOP-807: --------------------------------------------
1. & 2. I think these two are closely related and we should keep the same version for the data layout for fsimage and data-nodes. If we split them then we will have to support a table of compatible versions or something similar. Currently we have simple criteria: different versions are incompatible. I understand that some changes on the namenode do not necessarily make incompatible data-nodes running old versions and vice versa. But sometimes they do, and that is what DFS_CURRENT_VERSION is used for. 3. Yes there is a different version for Datanode protocol, which is DatanodeProtocol.versionID. I don't think we should split versions at this point, until we define our versioning approach in general. I agree, we should change the name of the constant. > 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
