Force HDFS to write blocks to specific host
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I want to force HDFS to write all blocks of a file to specific host. Is this possible and if it is what is the easiest way to achieve it?

Why? I am writing a new instance allocation algorithm for a cluster computing framework based on hdfs. Having all blocks of a file on one host makes comparing the new allocation system (which takes data locality into account) to the old one much easier, especially on a smaller cluster. 