Yes, the namenode is in charge of deciding the proximity by using DNSToSwitchMapping. On the other hand, I am exploring the possibility to let the client decide which data node to connect to, since sometimes network hierarchy is so complex or dynamic that we better leave it to the client to find out which datanode is nearest.
-Kevin On Wed, Aug 6, 2008 at 2:31 AM, Samuel Guo <[EMAIL PROTECTED]> wrote: > Kevin 写道: >> >> Hi, >> >> This is about dfs only, not to consider mapreduce. It may sound like a >> strange need, but sometimes I want to read a block from a specific >> data node which holds a replica. Figuring out which datanodes have the >> block is easy. But is there an easy way to specify which datanode I >> want to load from? >> >> Best, >> -Kevin >> > > DFSClient will choose a node that contains a replicas of the block for you. > The chosen node will be the nearest node to your client node. This method is > awesome. > plz let me know why you want to specify the datanode yourself :) >
