I need to implement COW for HDFS for a project I'm working on. I vaguely
remember it being discussed before, but I can't find any threads about
it. I wanted to at least check for interest/previous work before
proceeding. Hard links would work for me as well, but they are harder to
implement. I was thinking of adding the following to the client protocol:
public void cow(String src, String clientName, boolean overwrite,
LocatedBlocks blocks) throws IOException;
The call would simply create a new file and populate its contents with
the blocks contained in the LocatedBlocks.
Apart from fast copies, it also allows fast truncations and extensions
of existing files.
(This is not a hard link because it is possible that the set of blocks
may not correspond to any other file.)
Has such a thing been discussed before?
thanx
ben
