sendBlock() is used to read block and its metadata and stream the data to either
a client or to anot
close opened files.
Converts an IOExcpetion (not subclasses) to SocketException. This is typically
done to indicate to u
Returns true if we have done a long enough read for this block to qualify for
the DataNode-wide cach
Manage the OS buffer cache by performing read-ahead and drop-behind.
Read checksum into given buffer