MongoDB Sharding On One Machine

Question

Does it make sense to implement mongodb sharding with say 100 shards on one beefier machine just to achieve higher concurrenct write into the database as I am told, there is a global lock for each monogod.exe process? Assuming that is possible, will that aproach give me higher write concurrency?

Answer 1

Running multiple mongods on a machine is not a good idea. Every one of the mongod processes will try to use all the available memory, forcing other mongod's memory mapped pages out of memory. This will create an enormous amount of swapping in most cases.

The global database lock is generally not a problem as is demonstrated in: http://blog.pythonisito.com/2011/12/mongodbs-write-lock.html

Only use one mongod per machine (but it's fine to add a mongos or config server as well), unless it's for some simple testing.

cheers, Derick

Answer 2

I totally disagree. We run 8 shards per box in our setup. It consists of two head nodes each with two other machines for replication. 6 boxes total. These are beefy boxes with about 120GB of RAM, 32 Cores and 2TB each. By having 8 shards per box (we could go higher by the way this is set at 8 for historic purposes) we make sure we utilize the CPU efficiently. The RAM sorts itself out. You do have to watch the metrics and make sure you aren't paging too much but with SSD drives (which we have) if you do spill onto the disk drives it isn't too bad.