[ http://issues.apache.org/jira/browse/HADOOP-692?page=comments#action_12448875 ] Hairong Kuang commented on HADOOP-692: --------------------------------------
I think that what we only need is a rack distance matrix. So the storage is much less. But after I talked to Koji, it looks that it is hard to pre-compute an acurate distance between nodes. So a simple thing to do is assume that distance between two nodes in different datacenters is 3 or 4. No matrix is needed. I am working on designing an interface for network topology and an interface for replica placement policy. Will post them later. > 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
