NAS Hardware Selection (2012)

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Requirements

In 2012, my current storage server (NAS) was running full, so I wanted to buy a replacement server. I now have 4(!) external disk drives connected to my main desktop, and wanted to reduce that number. Also, I now often decommission smaller size disks which would still be useful in a server. So my first requirement was a system with at least four drive bays, but preferably more.

I first considered (in order from low price to high quality) a LaCie 5big network 2, Synology DS412+, Drobo FS, or IX Systems' FreeNAS mini and QNAP TS-559 Pro II. All these systems have four or five 3.5" disk bays, and range from €300 to €750 without disks. Add about €100 for each Terabyte disk.

Two requirements prompted my to build my own solution:

Services
The server should run the SMB and AFP protocols, as well as allow direct playing
Price
Building your own solution costs about the same for the bare system, but is more powerful and is cheaper per terabyte.

So I decided to build a custom FreeBSD (or FreeNAS) system. Not only would that give flexibility, it also allows me to play with ZFS, my favourite file system.

Choice of chassis

I mostly considered Fractal Design and Li Lian chassis, which offer a good wide choice in products. My first decision is what size I wanted to case to be. There are a few cases of less than 10 litre which allow 4 disks, like the [Lian Li PC-Q12]. However, that would limit myself to 2.5" disk bays. I wanted at least six 3.5" bays, and it was possible to achieve this in a mini-tower chassis of 20-25 litre. For comparison, a regular tower PC typically is 30-35 litre in size. Good choices in this size where the Fractal Design Array R2 NAS Chassis (with six 3.5" and one 2.5" disk bays) and the Lian Li PC-Q25 (with seven 3.5" and one 2.5" disk bays, where five of the 3.5" bays are hot swappable). Both these cases support mini-ITX and mini-DTX motherboard (the difference is that a mini-ITX has one expansion slot, and the mini-DTX has two expansion slots).

I picked the Lian Li PC-Q25 after reading a few favourable reviews. For those interested: the specification of the disk bays is somewhat confusing. The PC-Q25 can support eight disks at most. Five of these are in a hot swappable disk bay, the other three on a fixed metal plated. The middle location on the metal plate must be a 2.5" disk; the other locations can be either 2.5" or 3.5" disks.

Choice of CPU

My biggest hurdle was the choice between a low power CPU soldered on the motherboard or a regular pluggable CPU with some more power. CPU World certainly helped me compare the different CPUs. I naïvely thought that "a Atom CPU would do", not realising that there are many types of Atom CPUs, AMD alternatives, and also other juicy CPUs that only consume 30-35 Watt of power.

For starters, I looked up the benchmark of CPUs that I used previously. My 3-year old MacBook Pro benchmarks at 1501, while a consumer laptop my wife just bought now benchmarks at 2668. Those are the high-ends for me. The low end is my Soekris net6501 router which also runs FreeBSD. While it's load is near-zero for the switching routing and VPN it does now, it is sluggish when I want to compile a new tool. So that's my low-end. A colleague with his own NAS had a Sempron 140 at first, but recently upgrade to a Athlon II x2 250e so he could use it as a more spicy server.

Vendor Type Frequency #Core (Threads) L2+L3 cache TPD socket Benchmark
Intel Core 2 Duo E6600 2.4 GHz 2 4.0 MiB 65 W LGA 775 1501
AMD A8-3510MX 1.8 GHz 4 4.0 MiB 45 W FS1 2668
Intel Atom E640 1.0 GHz 1 (2) 0.5 MiB 3 W BGA 1466 (onboard) 250
AMD Sempron 140 2.7 GHz 1 1.0 MiB 45 W AM3 752
AMD Athlon II x2 250e 3.0 GHz 2 2.0 MiB 45 W AM3 1680
AMD G-T56N 1.6 GHz 2 1.0 MiB 18 W BGA 413 (onboard) 721
AMD E350 1.6 GHz 2 1.0 MiB 18 W BGA 413 (onboard) 726
AMD E450 APU 1.7 GHz 2 1.0 MiB 18 W BGA 413 (onboard) 740
AMD Fusion C-60 1.0 GHz 2 1.0 MiB 9 W BGA 413 (onboard) 563
Intel Atom D525 1.8 GHz 2 (4) 1.0 MiB 13 W BGA 559 (onboard) 714
Intel Atom N550 1.5 GHz 2 (4) 1.0 MiB 9 W BGA 559 (onboard) 568
Intel Atom N2800 1.9 GHz 2 (4) 1.0 MiB 7 W BGA 559 (onboard) 723
Intel Atom D2700 2.1 GHz 2 (4) 1.0 MiB 10 W BGA 559 (onboard) 818
Intel Celeron G530T 2.0 GHz 2 2.5 MiB 35 W LGA 1155 1800
Intel Pentium G620T 2.2 GHz 2 3.5 MiB 35 W LGA 1155 2261
Intel Pentium G630T 2.3 GHz 2 3.5 MiB 35 W LGA 1155 2344
Intel Pentium G640T 2.4 GHz 2 3.5 MiB 35 W LGA 1155 2400
Intel i3-2100T 2.5 GHz 2 (4) 3.5 MiB 35 W LGA 1155 3290
Intel i3-2120T 2.6 GHz 2 (4) 3.5 MiB 35 W LGA 1155 3088
Intel i5-2390T 2.7 GHz 2 (4) 3.5 MiB 35 W LGA 1155 4004

I was extremely impressed with the benchmark of the Intel Atom D2700 compared to its power usage. Since Atoms, like AMD E350s are only used as soldered onboard a motherboard, its availability is limited by the motherboards available. While making my purchase, no suitable motherboard was available with a Atom N2800 or D2700. I briefly considered a low power Intel core i3 variant, like the i3-2100T. After some consideration (including the $200 price increase for motherboard, cooling and separate CPU), I decided that my NAS wouldn't need that power, and decided that any low-power CPU with benchmark over 700 would do. That's comparable to an AMD Sempron, and good enough for basic file I/O and an occasional compile of a new kernel.

Choice of Motherboard

Mini-ITX has one expansion slot; mini-DTX has two expansion slots. So it's important to determine how many slots are needed. The main requirement for my motherboard was clearly the number of SATA ports. I needed as much as eight(!) SATA ports, and no motherboard had this many available. So I needed one expansion slot for a SATA card. Some (but not all) Jetway motherboards could use a SATA daughter board, so that would free the regular expansion slot. Unfortunately, the Jetways that support the SATA daughter board all have an old PCI instead of a PCI-express expansion slot, so that turned out to be a pig in a poke. I decided to rather buy a SATA adapter for a PCI-express slot. Nearly all modern CPUs have an internal graphics chips, so I didn't need a separate graphics card (it's a server after all). So my requirement was just one PCI-express slot, so I could use either mini-ITX or mini-DTX motherboard. In practice, a mini-DTX is harder to get by, so I ended up with mini-ITX.

Here are the issues I paid attentions at:

Brand
I was surprised to see that the better brands (like [Intel], [Supermicro] and to some extend [Jetway]) where not the best choices. Not only where they more expansive, they often didn't have a low-power product. So I mostly looked at [Asus], [ASRock], and to lesser extend [Gigabyte], [Jetway], [Zotac] and [Sapphire].
SATA II or SATA III
At the time of purchase, SATA III (aka SATA-600) was getting more common. SATA-300 is certainly good enough for a regular hard disk drive, though SATA-600 might be useful for a solid state drive.
Expansion slots
Nearly all motherboards has a PCI-expression version 2.0 x16 (sixteen lane) slot, but only x4 (four lanes) are wired. Despite the difference in advertisement as either "PCI-e x4" or "PCI-e 2.0 x16", there was no difference in practice. Attention was necessary: some motherboards still featured old PCI slots instead of PCI-express, while others supported the newer PCI-e 3.0 standard.
USB 2 or USB 3
At the time of purchase, USB 3 was getting more common.
Memory
All models support DDR3, although some use regular 240-pin DIMM slots and others the "laptop" 204-pin SO-DIMM slots. The amount of memory that can be installed, and the speed of the DIMMs did differ considerably,
Network
All models provided one gigabit Ethernet slot. Some motherboards has on-board wifi, but the later was a non-issue for me: wifi is way too slow (both in bandwidth and in latency) for a NAS.
mini PCI-e/mSATA
A few motherboards had a mini PCI-e slot. Such a slot has the same form factor as a mSATA slot, but the latter is not standardised and in practice most mini PCI-e can only be used to connect a wifi circuit, but not a mini SATA disk. If you want to connect a disk, check for mSATA support.
Video connector
I have seen any combination of VGA, DVI and HDMI. Most motherboards even support two (but not three) concurrent displays, although don't expect anything fancy from the graphics integrated with the CPU.
Serial port
I would liked a serial port. Most motherboard still offer an on-board serial connector, but few still provide an external RS-232 port. Those that do tend to be the more expensive non low-power motherboards.
FreeBSD support
It may be worth while to check support for certain hardware by the OS before purchase. This is particular true for expansion cards which usually feature a specific chipset.

The table below lists some of the better options. My first choice was the Asus E35M1-I, but I learned that it was no longer available just when I wanted to make the purchase. The E35M1-I deluxe and E45M1-I were a lot more expensive, and had one fewer SATA-600 port (it was replaced with eSATA).