Mongo replication sync to newer version
To upgrade to MongoDB 3.0 all members of a replica set must be running the previous major release (MongoDB 2.6). See: Upgrade a replica set to 3.0.

A replica set configuration mixing 2.4 and 3.0 nodes is not supported or tested and will likely lead to unexpected errors. Since you have 1.7TB of data, I would definitely follow the recommended upgrade instructions in the MongoDB documentation and upgrade all members one major release series at a time (2.4 => 2.6, then 2.6 => 3.0).

Since it sounds like you are starting from a single node, it would be more straightforward to:


Review the driver &amp; server upgrade notes and test driver compatibility for your target MongoDB server release. Drivers generally have a broader range of compaibility and should be upgraded first. There may be driver API changes required given the age of your current server version.
Take a backup of your MongoDB instance (perhaps using filesystem snapshots given your data size).
Upgrade your mongod as a standalone (2.4 => 2.6, 2.6 => 3.0) until you reach your destination release.
Convert your standalone to a replica set. When you add secondary members, this would be good timing to switch to the WiredTiger storage engine.


Ideally you should upgrade to a supported version of MongoDB (currently 3.4 or newer, although 3.4 will reach EOL in Jan 2020). Changes in successive releases have improved initial sync and 3.4 would be a much better starting point. MongoDB 3.4 also includes optional network compression for communication between mongod instances (which is enabled by default in 3.6+).