in some case you may not find the third node to place replica. Regards, *Stanley Shi,*
On Sun, May 11, 2014 at 10:55 AM, jianan hu <hujia...@gmail.com> wrote: > Hi everyone, > > See HDFS documents, It says "For the common case, when the replication > factor is three, HDFS’s placement policy is to put one replica on one node > in the local rack, another on a node in a different (remote) rack, and the > last on a different node in the same remote rack." > > Assume there are two racks A and B. According to rack awareness, the first > block is put in rack A, and the the other two replicated blocks will be > pushed into rack B. > > However, why not store the first and second replicas in the local rack > (A), and the last in a different remote rack (B)? Both two scenarios have > same network traffic. What's the disadvantage of it? > > Thanks. > > Best Regards, > Jianan >
