When data center or racks has un-even number of volume servers, the replication "110" may fail due to it randomly starting from one of the volume servers.

The work around is to use preferred data center. However, this needs manual operation.

For example, here is a user's case:

I start 6 volumes named "volume1" to "volume6" respectively. Set max=100. And the topology is: datacenter1: rack1:volume1, volume2 rack2:volume3 datacenter2: rack1:volume4, volume5 rack2:volume6 And then I want to upload some files with replication=111, but it dosen't work and show me error: Not enough data node found. I do have 2 different datacenter and racks, why it can't work?

v0.53 when growing volumes, additional preferred "rack" and "dataNode" parameters are also provided, works together with existing "dataCenter" parameter.

v0.53 fixed this bug.