Prem, Inline.
On Wed, Feb 8, 2012 at 12:58 AM, Jain, Prem <premanshu.j...@netapp.com> wrote: > Team, > > I have rack awareness configured and seems to work fine. My default rep > count is 2. Now I lost one rack due to switch failure. Here is what I > observe > > HDFS continues to write in the existing available rack. It still keeps two > copies of each block, but now these blocks are being stored in the same > rack. > > My questions: > > Is this the default HDFS behavior ? Yes. This is due to the default block placement policy. > What happens when the failed rack in back online ? Will HDFS automatically > rewrite blocks to the other rack ? No, would not do it automatically. > Or – Do I have to run the rebalance to make that happen ? Yes balancer may help. You'll also sometimes have to manually re-enforce the block placement policy in the stable releases presently, the policy violation recovery is not automatic: hadoop fs -setrep -R 3 / hadoop fs -setrep -R 2 / HTH. -- Harsh J Customer Ops. Engineer Cloudera | http://tiny.cloudera.com/about
