MongoDB 中不同的分片块大小

Question

我在 MongoDB Sharding 部署中遇到了一个问题。我有 4 个副本集，它们都有非常相似的块。但是它们每个块的估计数据都非常不同。

mongos> db.hadCompressed.getShardDistribution()

Shard rsmmhad01 at rsmmhad01/mmhad01a:27017,mmhad01b:27017
 data : 578.74GiB docs : 933429549 chunks : 23812
 estimated data per chunk : 24.88MiB
 estimated docs per chunk : 39199

Shard rsmmhad02 at rsmmhad02/mmhad02a:27017,mmhad02b:27017
 data : 55.18GiB docs : 91659330 chunks : 23812
 estimated data per chunk : 2.37MiB
 estimated docs per chunk : 3849

Shard rsmmhad03 at rsmmhad03/mmhad03a:27017,mmhad03b:27017
 data : 218.62GiB docs : 368024030 chunks : 23814
 estimated data per chunk : 9.4MiB
 estimated docs per chunk : 15454

Shard rsmmhad04 at rsmmhad04/mmhad04a:27017,mmhad04b:27017
 data : 406.31GiB docs : 640265568 chunks : 23814
 estimated data per chunk : 17.47MiB
 estimated docs per chunk : 26886

Totals
 data : 1258.88GiB docs : 2033378477 chunks : 95252
 Shard rsmmhad01 contains 45.97% data, 45.9% docs in cluster, avg obj size on shard : 665B
 Shard rsmmhad02 contains 4.38% data, 4.5% docs in cluster, avg obj size on shard : 646B
 Shard rsmmhad03 contains 17.36% data, 18.09% docs in cluster, avg obj size on shard : 637B
 Shard rsmmhad04 contains 32.27% data, 31.48% docs in cluster, avg obj size on shard : 681B

集群中的块大小定义为 64Mb。密钥分布如下：

        db.had
                shard key: {
                    "chkin" : 1,
                    "n" : 1,
                    "occ" : 1,
                    "nid" : 1,
                    "rtype" : 1,
                    "gid" : 1,
                    "hid" : 1
                }
                unique: false
                balancing: true
                chunks:
                        rsmmhad01   23812
                        rsmmhad02   23812
                        rsmmhad03   23814
                        rsmmhad04   23814

我的数据库中没有太多巨型对象（不超过 10 或 12）。

例如，将块大小从 64Mb 减小到 16Mb 是否有用？或者也许更改分片键会有帮助？

提前致谢。