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From "ryan rawson (JIRA)" <j...@apache.org>
Subject [jira] Created: (HDFS-942) Read and write metrics misleading/not helpful
Date Tue, 02 Feb 2010 22:28:18 GMT
Read and write metrics misleading/not helpful
---------------------------------------------

                 Key: HDFS-942
                 URL: https://issues.apache.org/jira/browse/HDFS-942
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: ryan rawson


the metrics wrap the entire readBlock() writeBlock() call (in DataXciever#run())

The problem with this is it includes the client socket read/write time. This means if a client
is slow at streaming a write block (eg: in hbase) then it skews the write metrics and makes
it look like the server is really slow.  Same problem with reads.

It would be nice if reads/writes meant actually local disk io and related processing (eg:
checksum verification/generation)

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