FAQ: What you should know about home servers.
As the saying goes, home servers are nice, but they are a lot of work. Before you get started, you should clarify a few questions.
(Image: c't)
- Peter Siering
- Christof Windeck
Home servers allow you to store all your files, media and resources in one central location. Before you buy, set up and maintain such a device yourself, you should clarify a few questions. Because there are more convenient alternatives, such as NAS.
What is meant by "home server"?
What exactly is a home server?
Home servers are not a clearly defined category of device. We are referring to an economical and typically also quiet and compact server for private use. Many people use a pre-purchased NAS (network storage) with a pre-installed operating system. Others opt instead for a Raspberry Pi or another single-board computer, a mini PC, a small server as a ready-made device or simply a desktop PC. Typically, home servers run open source operating systems.
NAS vs. home server
Is a NAS not a home server? What can a home server do better?
A NAS is a great home server! The devices from well-known brands such as Synology and Qnap, which have matured over several generations, are comparatively easy to put into operation. Their pre-installed Linux-based firmware can be operated via a web interface, while plug-ins from an app store extend the range of functions. Ready-to-use NAS receive updates automatically and containers and virtual machines (VMs) run on better devices. Compatibility lists for hard disks, SSDs, storage devices and network cards for retrofitting are available for many NAS. This reduces the risk of incompatibilities. Because the devices are produced in large numbers with standardized firmware, they work quite reliably and solutions can be found quickly for many problems.
Many NAS are economical and quiet, but still cool the hard disks well; this is not so easy to achieve with a DIY PC. Installing and replacing 3.5-inch hard disks is very easy with NAS, whereas quick-release frames for PC housings are expensive.
However, NAS no longer receive security updates after the support period has expired and it is not possible to install another operating system on most of them, at least not as easily. NAS for less than 500 euros (without hard disks) also have a maximum of four CPU cores and a maximum of 32 GB RAM.
Currently (mid-2024), a home server with PC hardware promises advantages if you want more and stronger CPU cores or more RAM. However, with a self-built home server, you have no warranty or guarantee for the entire system and have to install, securely configure and maintain the operating system yourself.
Does a home server make sense for me?
Should I buy a NAS instead of a home server? If the latter, will a Raspi be enough?
We cannot answer such questions because the individual requirements for a home server are very different. For many people, the NAS function of a Fritzbox with a USB SSD plugged in is enough. If you don't know what you need, then try it out first.
If you primarily want reliable mass storage in the local network, a NAS is the best choice. You can also combine a simple NAS with a Raspi. For starters, a Raspberry Pi 4 with 2 GB RAM is sufficient; it costs less than 75 euros including power supply unit, simple housing and MicroSD card and offers similar computing performance to NAS under 200 euros, which are equipped with ARM chips.
Home server purpose
Why do you need a home server at all?
There are plenty of answers and perspectives to this question: Anyone who switches between different PCs at home, such as a desktop and notebook, appreciates the server as a central data repository. If you travel a lot but don't want to entrust your data to a cloud, you can run comparable services on your home server, such as Nextcloud. For some, the home server also replaces the model railroad: configuring and trying out server services is exciting, instructive and perhaps also useful for the job.
Anyone who frequently repairs the PCs of relatives and friends will benefit from a self-installed network boot server, which keeps rescue media ready and replaces the USB sticks that are constantly disappearing. Of course, there are also many bread-and-butter services: Backup destination, movie and audio media library, eBook library, digital photo album, family mail server, smart home center et cetera.
Which home server OS?
Which operating system do you recommend for home servers?
In principle, almost any Linux distribution is suitable, preferably with a long support period (LTS: Long-Time Support, often five years). But there are also (Linux) operating systems specially designed for (home) servers, including Proxmox as a basis for virtualization, Unraid and Open Media Vault (OMV) with NAS functions.
If you can't decide for yourself which operating system your home server should have, then you might be better off buying a NAS. After all, most people who build a home server do so precisely because they want a specific operating system that won't run on a ready-made NAS.
Workload of a home server
How much work does a home server require?
The initial setup takes between hours and weeks, depending on the starting point. The instant home server in the form of a NAS or a specialized server distribution with some included services runs within hours. A Linux distribution set up by hand or a server set up as a home lab with many VMs tends to take days to weeks or is never finished at all.
Once a home server is up and running, regular attention is all that is needed: installing updates, checking log files for unusual activities or events. Both can be automated to a certain extent. With a server that provides services to the outside world, i.e. the Internet, this needs to be done more frequently and you should never rely completely on automation.
On a side note: A home server always shuts down when it is urgently needed, for example during movie night or when the mother-in-law is watching photos. Co-users should therefore know what to do to revive the device if the main person responsible is not available.
Home server costs
How much money do I need to spend on a home server?
In c't 3/2024, we published a proposed home server made from PC components that remains under 400 euros without hard disks. It has space and connections for four 3.5-inch SATA drives, a six-core processor, 16 GB RAM (upgradeable up to 128 GB), a 256 GB SSD for the operating system and two PCIe slots.
If you want to store more than 8 TByte of data, the hard disks are the most expensive individual components. A 12 TByte hard disk costs 200 euros. If very quiet operation is required, SSDs are better, but you will pay significantly more per terabyte.
Our design proposal consumes 17 watts of power in idle mode without hard disks. This results in an annual energy requirement of at least 150 kilowatt hours (kWh) in continuous operation, which costs just under 60 euros at a kilowatt hour price of 38 cents. Over five years, this adds up to 300 euros in operating costs. Economical operation is therefore very important.
Why is it only economical when idling?
Why does c't always harp on about power consumption in idle mode?
Home servers spend the vast majority of their operating time doing nothing. Even if you were to copy 50 gigabytes of data to and from your home server every day, for example, this would only take eight minutes with 1 Gbit/s Ethernet. Most home servers "work" for less than an hour a day, spending the remaining 95 percent of their running time dozing away. Therefore, the power consumption in idle mode dominates the average energy consumption per year.
Finding economical hardware
How do I find server hardware that is economical when idle?
The short answer: read c't! The long answer is complicated because the power consumption of a computer in idle mode depends on many factors and only a few data sheets contain information on this.
Above all, it depends on the combination of mainboard and power supply unit. Modern processors can switch to deep sleep states when idle, from which they wake up again within fractions of a second. However, this energy-saving sleep is only possible if the motherboard's BIOS configures everything optimally - and this is precisely what many board manufacturers neglect to do. As a result, many motherboards consume significantly more power than necessary. In addition, the motherboard should not have any unnecessary additional chips, such as PCIe PCI bridges or USB hubs.
The power supply unit, on the other hand, must convert voltage efficiently even at very low loads. This is not stated in its data sheet because the 80 Plus certification often only applies above 60 watts. In idle mode, however, economical desktop PC boards manage with 10 to 15 watts. At this low load, many PC power supply units unfortunately only achieve 60 to 70 percent efficiency and therefore waste more than 4 watts.
Mini-PC as a home server
Is a mini PC suitable as a home server?
Of course, as long as the computing power and features match your requirements. Mini PCs with mobile processors such as the well-known NUC series from Asus (previously Intel) get by with 4 to 6 watts in idle mode, have up to 14 CPU cores and 20 threads (hybrid processor with six P and eight E cores), can be equipped with up to 96 GByte DDR5 RAM (DDR4: maximum 64 GByte) and there are versions with two 2.5 Gbit/s Ethernet ports. However, most Mini PCs can only fit a maximum of two SSDs, i.e. neither 3.5-inch disks nor PCIe cards.
CPU performance for the home server
Which processor does a home server need?
That depends entirely on what you want to do with it. Many people are happy with NAS and the simplest two-disk devices have systems-on-chips (SoCs) with four older ARM cores (Cortex-A55). These chips calculate at a similar speed to 15-year-old PC processors, but this is sufficient for a file server with RAID 1 without encryption for full throughput via Gigabit Ethernet, i.e. around 100 MByte/s. You can also run a few less power-hungry services on such a device using plug-ins.
Most NAS with x86 processors under 700 euros are equipped with Intel SoC CPUs from the Celeron N, Celeron J, Pentium Silver and Alder Lake-N series (e.g. N100, N97), which were originally developed for cheap notebooks. A few NAS use similar embedded processors from AMD, such as Ryzen Embedded V1000. All of these chips perform much less than a current Core i5-14400 or the six-core Ryzen 5 4600G, which is around four years old and costs less than 100 euros. Nevertheless, NAS with 10-watt processors can run several services, VMs and containers simultaneously and also write encrypted data to their disks at full Gigabit Ethernet speed. They are also suitable for file servers with 2.5 or 10 Gbit/s, as long as not many users access them at the same time.
If you want to put several VMs on one server, you often want a separate CPU core or at least one thread (logical CPU core) per VM. If the individual VMs do not perform a lot of work, you can add more. The performance of the individual cores is not so important, at least with reasonably up-to-date processors they are fast enough.
RAM for the home server
How much RAM does a home server need and how fast should it be?
Here, too, it depends on what the home server is supposed to do. For a file server, 2 GB is enough. However, you are unlikely to install less than 8 GB because a DDR4 memory bar with this capacity costs just 25 euros. However, if you want to run a dozen VMs with 4 GB each, you need at least 48 GB.
The RAM speed is irrelevant for typical home server tasks, as long as there is enough available. It also doesn't matter whether you use one or two RAM channels - except in special cases that use the computing or 3D performance of a graphics processor integrated in the CPU. Just don't buy overclocker memory that only achieves its advertised clock frequency with XMP or EXPO profiles and increased operating voltage - this doesn't always work stably and drives up the power consumption. Overclocker DIMMs often have decorative plates, so it is better to use some without. You can get them up to the standard speed classes DDR4-3200 or DDR5-4800 without any problems.
ECC RAM for the home server
Are there advantages to installing memory modules with Error Correction Code (ECC) error protection?
Theoretically yes, in practice it is not clear and quite complex. In theory: ECC generates redundant information when writing, which can be used to correct by far the most common RAM errors when reading out, namely all single-bit errors. Two-bit errors are recognized, but not all of them are corrected.
ECC RAM is a typical function for professional servers; the remote maintenance chip of such devices also logs RAM errors, as these often indicate defects in a DIMM. However, ECC RAM can only be used if three conditions are met simultaneously: Not only does the system need the slightly more expensive ECC memory modules, but the processor must also have an ECC-capable memory controller and sit on a mainboard that has additional lines for ECC in the memory bus and whose BIOS switches ECC on.
Intel and AMD only enable ECC RAM in selected CPU versions, Intel only in combination with certain chipsets. ECC-capable hardware is often more expensive than normal PC technology and many server boards also consume more power when idle.
In our opinion, ECC RAM is unnecessary for home servers. Even affordable NAS without ECC RAM will run flawlessly for years. The widespread misconception that the ZFS file system should only be used on computers with ECC RAM was disproved years ago.
Which disks?
Can I put ordinary desktop PC hard disks in a home server? Or should they be special ones for NAS?
Neither: We now recommend buying hard disks designed for servers if they are to store more than 10 TByte each. This is because the special NAS hard disks are often more expensive, but mechanically identical. And the NAS disks with lower speeds, which used to be useful for private users and were therefore quieter and more economical, are hardly available beyond 12 TByte. The modern, helium-filled server disks are quite economical and quiet when idle, but rattle audibly when accessed - this can hardly be avoided, as they are also supposed to be firmly screwed in place.
Hard disks designed for desktop PCs are not intended for continuous operation and the manufacturers specify low upper limits for the amount of data transferred per year within the warranty period, for example only 55 TByte. For server disks, this "workload limit" is often ten times higher.
If you want to set up a RAID, it is better to buy hard disks with "Conventional Magnetic Recording" (CMR), i.e. the classic recording technology. Some drives use Shingled Magnetic Recording (SMR) with partially overlapping tracks. This can cause problems when repairing RAID arrays (RAID Rebuild [1]).
USB disks on the server
I would like a home server that is as compact as possible, but still has 3.5-inch hard disks for a lot of mass storage. Can't I just connect disks via USB?
We do not recommend this, unless you want a single economical USB SSD. If magnetic hard disks are to be used, we recommend installing SATA disks in a PC housing or NAS.
The external connection via USB cable harbors risks: Additional interference points, compatibility problems and the risk of someone accidentally pulling out the cable or knocking over upright disks.
USB hard disks with 2.5-inch drives are economical, but many use Shingled Magnetic Recording (SMR), which is not recommended for RAID. Some external 3.5-inch hard disks with USB connection have inefficient power supply units and consume up to 12 watts, some even several watts when not in use. This negates the biggest advantage of an economical Mini PC or Raspberry Pi.
External USB enclosures for several 3.5-inch drives can have even greater disadvantages: Loud fans, high power consumption, proprietary implemented RAID functions. The latter can lead to data loss if the USB enclosure fails and is no longer available.
N100 or Celeron board
Are PC mainboards with a soldered Intel Celeron J or N100 an economical and inexpensive alternative to boards with an interchangeable socket for Core i or AMD Ryzen?
Only in special cases, because many boards with such onboard CPUs are sloppily made and the processors have too few fast interfaces. It is therefore usually better to use an economical board with an interchangeable socket.
Celeron N/J, Pentium Silver and N100 only have two SATA ports each, few PCIe lanes and USB outputs. NAS manufacturers compensate for this with additional adapter chips. However, the aforementioned PC mainboards only provide a few PCIe slots with few and slow lanes. Retrofitted SATA adapters are comparatively expensive and some also consume several watts of power. Finally, the RAM on these chips cannot be upgraded as widely and flexibly as on motherboards with removable sockets.
(ciw)
