I'm building an "all in one" and I notice ESXi is picky about RAID controllers. It only likes hardware-based ones. Most onboard controllers, aka software RAID controllers, will not work. If you're not willing to install a hardware RAID controller, you can always run a single drive and hope for the best. So I'm looking at a new solution to the problem. New to me, anyway. I'm not exactly what to call these so I went with "Self-contained internal RAID" in the title. They are software based RAID controllers that perform RAID functions upstream from the SATA port they are plugged in to. Rather than configure it via the BIOS or OS levels, it is configured via a DIP switch usually on the rear of the unit. It is completely invisible to the OS so ESXi will never know that there is a RAID array behind the "SATA device" that it is booting off. I'm looking for something that supports mirroring (RAID1) two 2.5" SFF drives. SAS is preferred but SATA will do as well. Here are some items I found that can be installed inside my all-in-one box: This will take up to 5 devices and will do "RAID 0/1/3/5/10/ JBOD/CLONE". Fits in a PCI slot, but does not plug into the PCI port. Uses molex power connector. SYBA SY-PCI40037 SATA II (3.0Gb/s) Port Multiplier PCI Mounting Card This will take 2 devices and do RAID0/RAID1. Fits in a 3.5" slot. SANS DIGITAL IR12TB Internal RAID 0/RAID 1 2 bay 2.5" Hard Drive Enclosure This fits in a 5.25 and has 4x 2.5" SAS/SATA disks. Built in cooling fans. Support RAID 0, 1, 3, 5, 10 , Clone, Large, JBOD Patriot Convoy 425XL These are really hard to google which is why I had to make a post about it. Does anyone have any other ideas?