Map output packet form

[Pedro Costa <ps...@gmail.com>]

Hi,

I really like to know how a map output packet is formed on the local
disk at the Reduce and the Map side. I'm example, at the Reduce side,
the map output is copied to local disk also.
The problem is that I'm doing a message digest on the map output on
the map side and on the reduce side, and I get 2 different hash.

I thought that it could be from the checksum, but it isn't. So I don't
know what other fields, for ex. a timestamp, the map output could
have.

How is a map output packet formed?


Thanks,

PS: I really need this information and I can't find it on the web.
-- 
Pedro