set fs.trash.interval > 1
This specifies the time interval a file deleted would be available in trash. There is a property (fs.trash.checkpoint.interval) that specifies the checkpoint interval NN checks the trash dir at every intervals and deletes all files older than specified fs.trash.interval . ie say you have your fs.trash.interval as 60 mins and fs.trash.checkpoint.interval as 30 mins, then in every 30 mins a check is performed and deletes all files that are more than 60 mins old.
fs.trash.checkpoint.interval should be equal to or less than fs.trash.interval
The value of fs.trash.interval is specified in minutes.
fs.trash.interval should be enabled in client node as well as Name Node. Name Node it should be present for check pointing purposes. Based the value in client node it is decided whether to remove a file completely from hdfs or thrash it on an rmr issued from client.
The trash dir by default is /user/X/.Trash