[ http://issues.apache.org/jira/browse/HADOOP-692?page=comments#action_12448601 ] Bryan Pendleton commented on HADOOP-692: ----------------------------------------
Seems implied here, but I'll state it anyway, just in case it should be a separate issue: Reads should also be rack-aware. Requests to the NameNode can take the rack as an argument, and order the returned locations by rack locality. This implies that there should be a mechanism for a client to be told/discover what rack its on, too, so the argument to the datanode isn't the only place rack information is useful. > Rack-aware Replica Placement > ---------------------------- > > Key: HADOOP-692 > URL: http://issues.apache.org/jira/browse/HADOOP-692 > Project: Hadoop > Issue Type: Improvement > Components: dfs > Affects Versions: 0.8.0 > Reporter: Hairong Kuang > Assigned To: Hairong Kuang > Fix For: 0.9.0 > > > This issue assumes that HDFS runs on a cluster of computers that spread > across many racks. Communication between two nodes on different racks needs > to go through switches. Bandwidth in/out of a rack may be less than the total > bandwidth of machines in the rack. The purpose of rack-aware replica > placement is to improve data reliability, availability, and network bandwidth > utilization. The basic idea is that each data node determines to which rack > it belongs at the startup time and notifies the name node of the rack id upon > registration. The name node maintains a rackid-to-datanode map and tries to > place replicas across racks. -- 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
