Initialise mongodb replica set never completing - mongodb

Question

I am trying to intialise a mongodb replica set but whenever I add the new node it never makes it past state 3 (RECOVERING). Here is a snapshot from rs.status():
rs0:OTHER> rs.status()
{
"set" : "rs0",
"date" : ISODate("2015-04-27T14:09:21.973Z"),
"myState" : 3,
"members" : [
{
"_id" : 0,
"name" : "10.0.1.184:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 6899,
"optime" : Timestamp(1430143759, 9),
"optimeDate" : ISODate("2015-04-27T14:09:19Z"),
"lastHeartbeat" : ISODate("2015-04-27T14:09:20.133Z"),
"lastHeartbeatRecv" : ISODate("2015-04-27T14:09:20.160Z"),
"pingMs" : 0,
"electionTime" : Timestamp(1430127299, 1),
"electionDate" : ISODate("2015-04-27T09:34:59Z"),
"configVersion" : 109483
},
{
"_id" : 1,
"name" : "10.0.1.119:27017",
"health" : 1,
"state" : 7,
"stateStr" : "ARBITER",
"uptime" : 6899,
"lastHeartbeat" : ISODate("2015-04-27T14:09:20.133Z"),
"lastHeartbeatRecv" : ISODate("2015-04-27T14:09:20.166Z"),
"pingMs" : 0,
"configVersion" : 109483
},
{
"_id" : 2,
"name" : "10.0.1.179:27017",
"health" : 1,
"state" : 3,
"stateStr" : "RECOVERING",
"uptime" : 15651,
"optime" : Timestamp(1430136863, 2),
"optimeDate" : ISODate("2015-04-27T12:14:23Z"),
"infoMessage" : "could not find member to sync from",
"configVersion" : 109483,
"self" : true
}
],
"ok" : 1
}
Occasionally the infoMessage "could not find member to sync from" is visible on the new node. I note that the oplog on the current primary is only 0.12 hours (1.7GB) and that it is taking approx. 2 hours to copy over the majority of the dataset (as seen by network usage).
Is it correct to assume that the oplog must be greater than this 2 hour period for the initial sync to complete successfully?

Answer 1

It was indeed necessary for the oplog to be LARGER (in time) than the expected time to synchronise the data between two replicas. Disk is cheap so we increased our OPLOG to 50GB and restarted the sync, worked first time.