MongoDb arbiter can be used with multiple replicaSets?

Question

If I have different webpages for differents countries and each webpage have a mongodb replicaSet of 2-3 nodes, can I use an arbiter with more than one replicaSet so it votes in all?

Or I need to initiate an arbiter per replicaSet?

Answer 1

You can have multiple arbiter processes running on a single server (different ports). They are quite lightweight in terms of resources, as all they are doing is voting. You should look into starting the arbiters with the following arguments to keep them as lightweight as possible (from the Command Line Parameters Page):

• --smallfiles - Use a smaller initial file size (16MB) and maximum size (512MB)
• --nojournal - Disable journaling. In v2.0+, journaling is on by default for 64-bit

If you do not run with those options, then the arbiter will still work, but will pre-allocate data files before it knows that it is an arbiter.

Update (Jan 2018): Since this answer was written official guidance has been added to the docs for startup options of an arbiter, including options in the new config format. It can be found here.