I am replacing a member of a replica set (the new member has a different IP address).

What I am looking to do is as follows:

  • RSYNC the data directory of the existing secondary node to the new node.
  • Stop the existing node.
  • Map the existing hostname to the IP of the new node.
  • Start MongoDB on this new node with the replica set.

Mongo Version 3.2 and storage engine MMapV1

it is 3 member replica set.

My plan is to first replace arbiter with a new secondary node then. Do the procedure with on existing secondary node to replace this also.

Could someone please verify if the above steps make sense?

  • 1
    What version of MongoDB and (if 3.0+, what storage engine) are you using? In general you should not copy or rsync files from a running deployment as this is likely to introduce data inconsistency if files are being written to. You would be much safer reversing your first two steps: stop the existing secondary and then rsync the data files.
    – Stennie
    Commented Jun 9, 2016 at 13:49
  • @Stennie i have updated the question. My query is if i do not rsync and replace arbiter first with new machine with same host name will it rsync data from primary. Then i can go ahead with secondary with same procedure.
    – viren
    Commented Jun 10, 2016 at 4:24
  • I'm still not entirely clear what you're trying to do. Are you referring to rsync (the command line file-copying tool) or MongoDB replication initial sync? Are you replacing one member of the replica set or two (an arbiter and/or secondary)? Per my original comment, you should not use rsync on a running deployment. Initial sync is the normal process where you would rs.add() a new secondary. You cannot convert an arbiter into a secondary, as arbiters do not have any data.
    – Stennie
    Commented Jun 10, 2016 at 12:11
  • @Stennie i am not replacing Arbiter to secondary. I am removing it and adding fully data node. As per your suggestion i will use initial sync only as it will give more balanced accuracy for data. Could you please ass this as Answer so that i will close it.
    – viren
    Commented Jun 13, 2016 at 5:49

1 Answer 1


I think you can get what you want if you first rs.add() the new secondary, and when it's done you rs.remove() the arbiter.

There will be a brief period of thime with 4 nodes, howerever.

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