Dear Todd, By truncating i meant removing unused *blocks* from the namespace and let them be garbage collected. There will be no truncation of the last block(even if it is not full). This way , rather then garbage collecting all the blocks of a file , we will only be garbage collecting the remaining blocks.
-vidur > HDFS assumes in hundreds of places that blocks never shrink. So, there is > no > option to truncate a block. > > -Todd > > On Mon, Jun 21, 2010 at 9:41 PM, Vidur Goyal > <vi...@students.iiit.ac.in>wrote: > >> Hi All, >> >> In FSNamesystem#startFileInternal , whenever there is a overwrite flag >> set >> , why is the INode removed from the namespace and a new >> INodeFileUnderConstruction is created. Why can't we use the convert the >> same INode to INodeFileUnderConstruction. And we start writing to the >> same >> blocks at the same datanodes (after incrementing the GS) followed by >> either truncating the remaining blocks(if the file size decreases) or >> allocating new blocks (if the file size increases). This will decrease >> data redundancy and the job of garbage collector and will increase >> security. >> >> vidur >> >> >> >> >> -- >> This message has been scanned for viruses and >> dangerous content by MailScanner, and is >> believed to be clean. >> >> > > > -- > Todd Lipcon > Software Engineer, Cloudera > > -- > This message has been scanned for viruses and > dangerous content by MailScanner, and is > believed to be clean. > > -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.
