Hyperconverged Supermicro a2sdi-4c-hln4f

This howto aims at describing the choices and the build of a compact homelab with a hyperconverged chassis based on a Supermicro A2SDi-4C-HLN4F motherboard. The hypervisor OS will be Slackware64-current (with Qemu/KVM for virtualization), the storage will be provided by a Truenas core VM (thanks to pci-passthrough) and network orchestrated by an OPNSense VM.

Motivations

Why such a motherboard with a modest 4 cores Intel Atom C3558 ? Let's see the advantages :

• obviously, it's very compact (mini-itx form factor)
• up to 256 GB ECC RDIMM RAM supported
• the CPU has a very low TDP (~ 17W), so no need for a fancy and potentially noisy cooling solution
• 4 * 1 Gb/s Ethernet ports (cool for a network appliance such as OPNSense and there's no need for 10 Gb/s for this project)
• dedicated IPMI Ethernet port
• the SATA ports are provided by two distinct PCIe lines (see below, very important for pci-passthrough and no need for an additionnal HBA card)

A2SDi system block diagram

Well, the system has drawbacks too :

• the CPU power will not be extraordinary
• it's not possible to put a fan directly on top of the CPU heatsink (more on that later)
• no external USB 3.0 ports (ony one "internal", on the motherboard itself) ; this is desirable to plug an external HDD for local backups (USB 2.0 is too slow)

2.5 or 3.5 inches drives ?

What is required for this project :

• Hypervisor OS on RAID 1 with two drives
• 4 TB of encrypted data with a minimum of resilience (at least RAID 1 or RAID 5, RAID 10 or RAID 6 desired)
• it is recommended not to exceed 80% of the capacity of a ZFS filesystem, so, for 4 TB of usable data, 5 TB of raw capacity is required
• all disks easily accessible from the front of the chassis

Choosing between 2.5 (SFF) or 3.5 (LFF) inches is not so easy. Obviously, for raw capacity over a gigabit network, LFF HDD are unbeatable in terms of price. In France (as of march 2021), it costs ~ 80 euros for a 2 TB NAS 3.5 LFF HDD ... Same price for a 1 TB NAS SFF HDD. Moreover, SFF HDD simply doesn't exist for consumer NAS systems (enterprise SFF HDD over 2 TB exist but are way too expensive). LFF HDD are a clear winner ? What about chassis size, cooling and noise ?