Actually i have an application which read data  often  rather than
inserting data from/to mongoDB database...and i set up a sharding
environment for my mongoDB database ( 3 shard) but for the first system
test (beta test) mongos only read data from one shard for a really long
because the chunk still not splitting (i use 64 MB chunk size at that time)
and make the shard load high. after that i try to decrease the chunk size
to 32 MB.and finally the read data load balance in each shard.

Is it fine if i use the smaller chunk size first and after i found out that
the insert rate is increase, i increase it to reduce the network load due
to the frequently chunk movement? What is the tradeoff from my action?

Sorry for my terrible grammar and english :D