SSD-cached storage at VPS node
I am going to rent a dedicated server for several VMs with Proxmox + KVM on Ubuntu.
Storage: 4 x 4TB hard drives at hardware RAID10 (random controller) from Hetzner.
The question is how to speed up i/o. Pretty large mongo db with concurrent writes.
Idea is to add one (or two?) NVMe cards for cache and to use software like BCache, Flashcache, EnhanceIO, dm-cache, etc.
The question is: 1. Is there any sense to add NVMe for cache? 2. Which cache software will be the most efficient and reliable in this case?