I have an OWC Thunderbay4 Mini loaded with 4 Samsung 850EVO 1TB SSDs configured in RAID 0. It's screaming fast, and performs well for my needs.
However, Spotlight searches on the volume can be inconsistent. I need to add the volume to Privacy, then remove it to force a Spotlight re-index. Even then, it sometimes omits some of the most recent files.
Is there something I can do to make sure that the volume is constantly indexed?
Spotlight is an OS X activity. The problem you are encountering is not related to SoftRAID. SoftRAID's driver does not manage files in any way, so is not involved with Spotlight activities.
You may need to "repair" your OS X installation, either with a combo updater
https://support.apple.com/downloads/combo
Or perhaps a clean installation.

