So, traditional databases can be set up on a RAID 0 with multiple volumes to increase throughput but I think there will likely be a trade off with SiaCoin depending on how the hosts are set up that the data is stored.
For fault tolerance, up to 7 of the 21 hosts could fail and data would still be recoverable. So the trick would seem to be judicious in your host selection so that they meet whatever requirements there may be.