On https://docs.opsmanager.mongodb.com/v1.8/tutorial/prepare-backing-mongodb-instances/

1) Change "Must run MongoDB 2.6.0 or later." to "Run MongoDB 2.6 on version 2.6.6 or later, or MongoDB 3.0 on 3.0.6 or later"

2) it is time to tweak the wording from "Must use the MMAPv1 storage engine." to "See storage engine considerations" which should link to a section below that states:

"Considerations when choosing a storage engine for the Ops Manager Application and Backup Databases:

MMAPv1 and WiredTiger have different performance characteristics. The Ops Manager Application and Backup Database schema was very carefully designed to achieve maximum performance on MMAPv1. Storage is also minimized on MMAPv1 in the Backup Database's Blockstore as all the blocks are already compressed and padding is disabled, so there is typically no further storage benefit to be gained by taking advantage of WiredTiger compression. Therefore, while WiredTiger outperforms MMAPv1 on typical workloads, we recommend MMAPv1 for the unique Ops Manager workload. Backups of insert-only MongoDB workloads that benefit from high levels of block-level de-duplication in the Backup Blockstore may see a compression-based storage reduction when running the Backup Database on the WiredTiger storage engine, however."