In doing this year's budgeting, I need to estimate the capacity needs for next year. We are planning on needing to shard our MongoDB Replica Set out to 4-shards, but I have the disk capacity needs for that planned.

The overall data set size is expected to be 600GB, but I am accounting for each of the 4 shards to be 200GB, in order to account for the possibility of unbalanced shards.

What I cannot find, is how much storage is required for my (3x)Config Servers and (3x)MongoS servers. I have been through the MongoDB docs and searched Google for "mongos disk capacity planning" to no avail. Can anyone point me to documentation, guidance, or at least personal examples of how much storage is required for their Config and MongoS servers?

1 Answer 1


Your MongoS will not store any local data and your Config servers config db will be minimal and depend on the number of collections sharded. I'm seeing a config db size of < 512M for a 8 shard setup ( roughly 800G ) with 5 sharded collections.


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