CODEWITHSUNDEEP
mongodbsharding
Steve Westwood
Steve Westwood

Reputation: 43

When I create sharded collections, should it create chunks across more than 1 shard?

I am trying to confirm whether the sharding and chunking behaviour is correct in my MongoDB instance.

We have 2 shards, each with a replica set, and have: (a) Enabled sharding using sh.enableSharding() command for my database (b) Added an hashIndex to a new collection via db.X.ensureIndex() command (c) Added the sharded collection to my database via sh.shardCollection() command.

When I run sh.status, I notice that only one of my two shards contains chunks, implying that my data is not distributed. I have added a couple of documents to test processing, but I still only see 1 chunk. Is this the correct behaviour? Intuitively, I would expect more 1..n chunks in each shard.

Thanks in advance,

Steve Westwood

Upvotes: 0

Views: 325

Answers (1)

Adam Pridmore
Adam Pridmore

Reputation: 163

Mongo will only start to split data across chunks when the first chunk has reached a certain size. When there are less than 10 chunks it will split when a chunk grows above about 16mb. When there are more chunks it will split them at 64mb.

So I expect you don't have enough data to trigger a chunk split.

You can override these chunk size values with the chunkSize option to the mongos, which can be useful for testing.

Upvotes: 1

Related Questions