You observed that the number of spilled records from Map tasks far exceeds the number of
map output records. Your child heap size is 1GB and your io.sort.mb value is set to
1000MB. How would you tune your io.sort.mb value to achieve maximum memory to disk
I/O ratio?

A.
For a 1GB child heap size an io.sort.mb of 128 MB will always maximize memory to disk
I/O

B.
Increase the io.sort.mb to 1GB

C.
Decrease the io.sort.mb value to 0

D.
Tune the io.sort.mb value until you observe that the number of spilled records equals (or
is as close to equals) the number of map output records.