linux - 为什么分片需要很多存储空间？

Question

我正在测试 mongodb 的分片功能，我将 30278845 文档插入到集合中，现在磁盘状态是

# ls
configDb  shard1-1  shard2-1
# du -csh shard1-1/
87G     shard1-1/
# du -csh shard2-1/
90G     shard2-1/

这是收藏文件，我不明白为什么会占用这么多空间？

mongos> db.testtable.find()
{ "_id" : ObjectId("51a1ce8a4c8b466d008b6780"), "name" : "6BScn0", "age" : 13 }
{ "_id" : ObjectId("51a1b9920c30fb7000000000"), "name" : "HXnAZv", "age" : 13 }
{ "_id" : ObjectId("51a1ce8a4c8b466d008b6910"), "name" : "kRZXj3", "age" : 13 }
{ "_id" : ObjectId("51a1b9920c30fb7000000001"), "name" : "3K4lev", "age" : 13 }
{ "_id" : ObjectId("51a1ce8a4c8b466d008b6974"), "name" : "A0D2wo", "age" : 13 }
{ "_id" : ObjectId("51a1b9920c30fb7000000002"), "name" : "AmhkRV", "age" : 13 }
{ "_id" : ObjectId("51a1ce8a4c8b466d008b6a3c"), "name" : "17mVkj", "age" : 13 }
{ "_id" : ObjectId("51a1b9920c30fb7000000003"), "name" : "E8t6Jf", "age" : 13 }
{ "_id" : ObjectId("51a1ce8a4c8b466d008b6b68"), "name" : "0u8vhV", "age" : 13 }
{ "_id" : ObjectId("51a1b9920c30fb7000000004"), "name" : "ZNCzlL", "age" : 13 }
{ "_id" : ObjectId("51a1ce8a4c8b466d008b6cf8"), "name" : "DmCJRp", "age" : 13 }
{ "_id" : ObjectId("51a1b9920c30fb7000000005"), "name" : "s3JPDJ", "age" : 13 }
{ "_id" : ObjectId("51a1ce8a4c8b466d008b6fb4"), "name" : "C9GE0B", "age" : 13 }
{ "_id" : ObjectId("51a1b9920c30fb7000000006"), "name" : "kHtp3I", "age" : 13 }
{ "_id" : ObjectId("51a1ce8a4c8b466d008b7018"), "name" : "nrcUYc", "age" : 13 }
{ "_id" : ObjectId("51a1b9920c30fb7000000007"), "name" : "VD4cYW", "age" : 13 }
{ "_id" : ObjectId("51a1ce8a4c8b466d008b720c"), "name" : "bK6HdH", "age" : 13 }
{ "_id" : ObjectId("51a1b9920c30fb7000000008"), "name" : "7C5AJO", "age" : 13 }
{ "_id" : ObjectId("51a1ce8a4c8b466d008b75f4"), "name" : "5ZdZDj", "age" : 13 }
{ "_id" : ObjectId("51a1b9920c30fb7000000009"), "name" : "QIBshX", "age" : 13 }
Type "it" for more

Answer 1

我重新阅读了有关 mongodb 存储的文档，并弄清楚了，文档说

在 64 位安装中，默认分配大约是磁盘空间的 5%。

我的磁盘状态是

/dev/sda7             1.8T  176G  1.5T  11% /

我在磁盘上有两个分片，总共是 90*2G，这就是原因 :)