The default number of replication threads is set to 5 by default. You should take into consideration the number of search peers, the network bandwidth between search head and peers as well as the size of the bundles when changing this value. Consider increasing it if you have a lot of peers, the link between SH and peers is slow and the bundle are large. If you have SSL enabled between SH and peers you will incur a high cpu load during the transfer because the bundle will be encrypted, compressed and sent to the peers by X thread in parallel.
