Re: Confused with Chunksize

[Gianfranco]

When you decreased the chunk size, chunk got split and moved between the shards.

But If you increase it back, chucks cannot merged or combined.

http://docs.mongodb.org/manual/administration/sharding/#chunk-management

When data is moved, there's some state resetting in mongos. Queries that used to hit a given shard for a migrated chunk, now need to hit a new shard. This state-resetting isn't free, so we want to move chunks infrequently (pressure to move a lot of keys at once). However, the actual moving has a cost that's proportional to the number of keys you're moving (pressure to move few keys).

http://www.mongodb.org/display/DOCS/Sharding+Administration#ShardingAdministration-ChunkSizeConsiderations

On Wednesday, October 3, 2012 11:04:32 AM UTC+1, aryton wrote:

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