Hello amuka79,   The BOSS  (Boot Optimized Storage Solution) card is recommended for hypervisor: Part# 403-BBUC - BOSS controller card, low profile, Customer Kit (I don't think it comes with the m.2 drives you will also need to purchase. Please check with sales.)   BOSS-S1 User's Guide BOSS-S1 is a simple RAID solution card designed specifically for booting a server's operating system. The card supports up to two 6 Gbps M.2 SATA drives. [URL]  
I've got a PER6415 running VMware ESXI 6.5 on USB drive. We want to upgrade to ESXi 7.0 but it does not support USB or SD cards anymore so we need to move it to a more persistent storage (SSD and so forth). I have 6 used front bay slots with 2.5" SAS drives and 2 remaining slots that I dont want to use. My plan is to clone the existing ESXi image from he USB drive to an SSD drive and then attach to a PCIE SSD adapter.  Is this possible and are there any specific PCIE SSD adapter that is bootable?
PCIE SSD adapter card for PER6415