always have killed or failed task in job when running multi jobs concurrently

when hadoop running multi jobs concurrently, that is when hadoop is busy, always have killed tasks in some jobs, although the jobs success finally. anybody tell me why? -- Regards Junyong

hadoop jobs stop at state 4(prepare)!

three jobs in my hadoop cluster have stopped at state 4 for five hours!!! my hadoop become more and more slow sice i begin setup it, i think mybe because the hadoop filesystem become more and more larger? here is bin/hadoop fs -count result: 401141 824522 659714994647