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)

Hardware

2.5 or 3.5 inches drives ?

What is required for this project :

• mini tower format chassis
• Hypervisor OS on RAID 1 with two drives
• at least 4 TB of encrypted data with a minimum of resilience (mirror or raidz1 / raidz2 ...)
• 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 drives 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 over 2 TB simply doesn't exist for consumer NAS systems (enterprise SFF HDDs exist but are way too expensive). LFF HDD are a clear winner ? What about chassis size, cooling and noise ?

At this point, there are two choices :

• 2 * 500 GB SFF SSD (RAID 1 for hypervisor and VMs OS) plus 2 * 6 TB LFF HDD (mirror storage)
• 2 * 500 GB SFF SSD (RAID 1 for hypervisor and VMs OS) plus 4 * 2 TB SFF SSD (raidz1 storage)

The most reasonable would be to use LFF HDD but silent operation with a tiny chassis are very important, so let's stick with the "unreasonable" configuration !

Cooling the CPU

As seen earlier, a standard CPU fan cannot be fitted on the heat sink.

final system

• Chieftec mini tower case
• Supermicro A2SDi-4C-HLN4F
• 64 GB DDR4 RAM ECC (RDIMM)
• ToughArmor MB992SK-B for hypervisor and VMs OS with 2 * WD SA500
• ToughArmor MB994SP-4SB-1 for data storage (with fans off) with 4 * Crucial MX500
• PCIe card with 2 * USB 3.0 ports