Users upgrading from 2.4 will incur significant performance penalties with w:0 writes through mongos, as mongos waits for a response from the shard(s) primary (where it previously didn't) before accepting the next client operation.
Ideally, users can upgrade from <= MongoDB 2.4 and not incur performance penalties for w:0 write operations.
- duplicates
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SERVER-14003 2.6 mongos does not support overlapped writes at w:0
- Closed