Data file WiredTiger (*.wt) are high on one Mongo shard

Hi Experts,

I have 10 shards MongoDB cluster on AWS EC2 machine with mongo version 3.6.11, in that rate of increase of data files on one of the shard is high, I want to know when collection & index wt files will generate. Number of DBs, collection, indexes and data size are less in that shard as compare to others. This is causing me connection spike issue. Details are as below:

No of DBs in each shard:
6171 DBs in db0
6182 DBs in db1
6142 DBs in db2
6260 DBs in db3
5823 DBs in db4
5694 DBs in db5
5181 DBs in db6
5052 DBs in db7
2117 DBs in db8
2156 DBs in db9

Index Size of each shard:
Index size on db0 in bytes = 100757651456
Index size on db1 in bytes = 91092033536
Index size on db2 in bytes = 100978843648
Index size on db3 in bytes = 89782575104
Index size on db4 in bytes = 85394440192
Index size on db5 in bytes = 87024951296
Index size on db6 in bytes = 89708388352
Index size on db7 in bytes = 87563587584
Index size on db8 in bytes = 47799222272
Index size on db9 in bytes = 48416301056

wt file counts:
Data dir file counts for db0 : 115912
Data dir file counts for db1 : 103572
Data dir file counts for db2 : 101192
Data dir file counts for db3 : 115447
Data dir file counts for db4 : 80676
Data dir file counts for db5 : 89648
Data dir file counts for db6 : 115500
Data dir file counts for db7 : 104279
Data dir file counts for db8 : 120104
Data dir file counts for db9 : 151194

Please let me know, why and when wt files will create or increase, data size for this shard is approx 250GB and for others it is around 365GB, so data in collection is also not high to create more wt files for a collection. I am using xfs mount for data directory, mongo version 3.6.11 & server is ubuntu1604. Thanks in advance


Hi expert,

may I get solution for this.


Hi Sourabh,

As per my understanding , .wt file created for every new collection and index.