In 64-bit MongoDB When the sharding process starts from one shards to another shards? -

i undergoing unit test in 64-bit mongodb in 64-bit linux machine.i have 2 shards both of shards configured in local machine testing purpose.so when sharding process starts on 1 shards another?.whether have give size limit first shard once size exceeded in first shard go next shard?please give me solution.

advance thanks,

data in given collection stored in "chunks" of data in contiguous/order preserving manner, default 200mb in size. once chunk reaches size, split 2. , once shard has imbalance of data, mongo start rebalance data moving chunks around between shards - it's these "chunks" of data being moved.

so default, need populate collection reasonable amount of data in order end multiple chunks of 200mb start moved around between shards. testing purposes, can change chunk size (e.g. first time played around it, set 1mb) setting --chunksize argument on mongos process. means need few mb of data in collection before start seeing sharding kick in.

here's great example setup testing out sharding explains chunksize:
http://www.mongodb.org/display/docs/a+sample+configuration+session

here's introduction sharding:
http://www.mongodb.org/display/docs/sharding+introduction#shardingintroduction-chunks