[ http://issues.apache.org/jira/browse/HADOOP-158?page=comments#action_12413911 ]
Doug Cutting commented on HADOOP-158: ------------------------------------- I would think that random allocation would make collisions more likely, not less. We always know which block ids are used by complete files. The concern is only about block ids which have been recently allocated to a file, but the file is somehow not yet complete. So, with sequential allocation, a collision can only happen if the probe key (the next block id to allocate) wraps all the way around before a file is completed, while with random allocation it can happen much more frequently. We simply have to make sure that probe key increments are logged to the edits file along with other file system changes. Am I missing something? > dfs should allocate a random blockid range to a file, then assign ids > sequentially to blocks in the file > -------------------------------------------------------------------------------------------------------- > > Key: HADOOP-158 > URL: http://issues.apache.org/jira/browse/HADOOP-158 > Project: Hadoop > Type: Bug > Components: dfs > Versions: 0.1.0 > Reporter: Doug Cutting > Assignee: Konstantin Shvachko > Fix For: 0.4 > > A random number generator is used to allocate block ids in dfs. Sometimes a > block id is allocated that is already used in the filesystem, which causes > filesystem corruption. > A short-term fix for this is to simply check when allocating block ids > whether any file is already using the newly allocated id, and, if it is, > generate another one. There can still be collisions in some rare conditions, > but these are harder to fix and will wait, since this simple fix will handle > the vast majority of collisions. -- 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
