performance - mongos slow after shardcollection added -


so have big collection 100 million records. need shard , i'm doing testing. found out performance decreased when running query on collection sharded, 1 shard.

i started mongos , added mongod shardcluster (so 1 server yet). when .explain() query 230000 return values, response time 800ms, same when query directly on mongod server. enable sharding specific collection, still same response times (800ms). enable sharing cluster , add shard key, response times increased 1400ms exact same query on mongos. when query directly on mongod response times still 800ms. other queries collections not sharded show equal response times on mongos , mongod, once collection sharded, response times increased (almost doubled).

what happened , why response times got worse? helding shard. need 2 shards equal performance 1 single big server, should not essence of sharding...


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