Designing an unRAID server

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An unRAID server is made up of a standard set of parts. This page discusses some of the general issues that need to be considered when designing your server, and how they influence the parts that you choose.

The Hardware Compatibility page should be read in conjunction with this page. It lists brands and models that have been reported by users to work with unRAID builds, and includes recommended builds, with links to online stores in several countries.


General considerations

Reliability

Security of data is paramount with any filestorage system, including unRAID. Although unRAID provides for a parity disk to protect against data loss or other malfunction, it is best to reduce risk further by using reputable brands, and products that have been tested by other users.

Location

The place where the server will be stored influences purchase and design decisions, both aesthetically and practically. Full tower and mid tower cases have plentiful space for hard drives, but are bulky and have a large footprint; if the server is to be in plain view, a smaller form factor or a more expensive and better looking case may be more acceptable. If the server is to be stored in a cupboard/closet where airflow is limited, additional cooling may need to be installed.

Usage

For a standard unRAID server, focused on reading and writing files and calculating parity data, high-specification parts are not required. Instead, many unRAID servers use low-power, single core CPUs and 5400rpm hard drives.


Case

Several types of case are available

  • Full tower case: The largest tower-form case, able to hold the greatest number of components. Typical dimensions: 24" x 10" x 23”
  • Mid tower: Commonly used for unRAID builds. A mid tower case typically has space for up to 9 hard drives, but with 4-in-3 or 5-in3 devices can hold up to 12-15 drives. Typical dimensions: 20" x 8" x 17”
  • Mini tower: Typical dimensions: 17" x 6" x 14”
  • Desktop
  • Rackmount


Power supply unit (PSU)

Main article: PSU

The three key considerations when choosing a PSU are:

  • That the PSU can deliver sufficient power to the system.
  • That the PSU has a single 12v rail. i.e. it delivers its full load of power from any one of its cables.
  • That the PSU is efficient. Look for a PSU with an efficiency rating of 80plus or better.


Motherboard

unRAID supports both Intel and AMD processors, and a wide variety of motherboards are compatible with the system.

When researching motherboards, consult the Hardware Compatibility guide to ensure that the Network Interface Card (NIC) is supported by unRAID.

Also consider:

  • Number of SATA ports: motherboards with 6 SATA ports – and hence support for 6 SATA drives – are often recommended, as a good sized system can be built before expansion cards are required.
  • PCI expansion slots: used to expand beyond the motherboard’s base SATA ports. Note that on some motherboards, PCIe x16 slot supports only video cards.
  • Onboard video: as a monitor needs to be attached to the server for its first boot, and for occasional troubleshooting, this will eliminate the need to purchase a separate video card. Note this is not a requirement for motherboards using KVM over IP methods, such as the IPMI protocol.


CPU

As unRAID is not a CPU-intensive system, low-power single-core CPUs are often recommended.

If the server will be used for CPU-intensive tasks, such as torrents, video encoding or virtual machines, higher specification CPUs with dual cores will be advantageous.

Check that the CPU socket type is compatible with your motherboard.

An aftermarket cooler is not needed for unRAID, but if you buy an OEM processor (such as Intel's enthusiast platform CPUs (i7-3820, 3930K, 3960X, 3970X), AMD's FX 9-series (FX-9370, 9590), or the Xeon E5 LGA2011 series), you must get an aftermarket cooler because the manufacturer does not provide one.

unRAID does NOT support overclocking, so you do not need a K-skew or an unlocked processor.

Memory

For most unRAID builds, 2GB of RAM is more than adequate. If the server will be used for tasks such as running torrents or virtual machines, at least 4 GBs of RAM is recommended.

Technically 2x1GB RAM sticks in Dual Channel mode is a bit faster than 1x2GB, but the extra speed won't be apparent in the unRAID environment. Using 1x2GB allows more room for future expansion (up to 4 or 8 GB).

ECC RAM is recommended if the server will be running 24/7, or provides mission critical services. For other uses, cheaper non-ECC RAM is likely to be appropriate.

Check that the memory matches the motherboard's DIMM slots. Also, check if your motherboard chipset supports ECC RAM. A list of chipsets that support ECC RAM is shown below.

Supported Chipsets: AMD 970, 990FX, 980G, 760G, Intel X79, (all of Intel and AMD's server/workstation chipsets)

Unsupported Chipsets: Intel H61, P67, H67, Z68, Q67, Q65, B65, Z77, Z75, H77, Q77, Q75, B75, Z87, H87, B85, Q87

PCI expansion cards

As unRAID has its own support for hard drives, a separate RAID Controller is not required for the system. Just look for a motherboard with plenty of SATA ports.

If the system you are building requires more SATA ports then your motherboard has, then purchase a separate SATA controller.

NOTE: A SATA controller is not a RAID controller. All a SATA controller does is add more SATA ports to your array.

A quality SATA controller can be found here: SYBA SI-PEX40064 PCI-Express x1 Low Profile Ready SATA III (6.0Gb/s) Controller Card

Also, a separate graphics card is not required by unRAID. Only purchase one if your motherboard does not have onboard video (i.e. an AMD _70 or _90FX motherboard). There is no need for a high-end graphics card because unRAID only renders a basic UNIX console, so purchase a low-end card such as this one: MSI GeForce 210 512MB GDDR2 PCI Express 2.0.

NOTE: Some AMD AM3/AM3+ boards do have onboard video, but the chipsets do not usually support SATA III (6Gb/s). They usually end in either a 60G or an 80G.

Hard drives

The two key considerations when selecting hard drives are size and rotation speed.

Size

The sizes of drives purchased often depend upon the current ‘sweet-spot’ for £/$ per GB. There is a balance between the use of fewer, large capacity drives to reduce the amount of power required by the system, with an increased risk of large-scale data loss if two drives fail at the same time.

The parity drive must be the largest drive, or equal in size to the largest data drive(s).

Rotation speed

Green or LP (low power) drives – 5400 or 5900 rpm – are often recommended both for parity and data because they are cooler, quieter, and use less power than higher speed drives.

Improved performance can be seen if both the parity drive and the data drives are of a faster rotational speed: having a 7200 rpm parity drive with all 5400 rpm data drives will not be of benefit. There is a compromise – having a 7200 rpm parity drive and one or more 7200 rpm data drives (the drives that will be used most-used) as well as some 5400 rpm data drives. In this case, writes to the 7200 rpm data drives will be faster, and writes to the 5400 rpm data drives will be slower.

A cache drive is optional, and is only available with an unRAID Plus or Pro license. Using a 7200 rpm cache drive will improve the server's perceived write speed as all writes will initially be going to the faster cache drive. A cache drive will only help with perceived write speeds, not read speeds. However, a cache drive only defers the inevitable slow write into the parity protected array until later in the night when the server is otherwise idle.

Temporally spacing out purchases of drives will decrease the chances of getting a bunch of drives from the same (potentially bad) batch. Mixing and matching drive makes, models, and retailers can help as well.


Hard drive stackers

See the SATA Hard Disk Stackers page for examples of modules that are available

To increase the number of drives that can be held in a case, 4-in-3 or 5-in-3 stacker modules can be used to fit 4 or 5 hard drives into the space of three 5.25” drive bays. These modules typically come in two forms:

  • Cheaper, dumb ‘cages’ that require the drives to be screwed into place and cables attached directly to the drives.
  • Backplanes - these often have dedicated fans, and offer condensed power slots (meaning fewer of the PSU's power cables will be used). Some backplanes also offer SAS ports instead of SATA ports. SAS ports can help with cable management as 4 SATA cables are combined into a single SAS cable. These SAS cables are generally more expensive than SATA cables, and also pose the risk of taking up to 4 drives out of commission if they should fail.


Cooling

Airflow and temperature regulation are extremely important in maintaining the health of the drives. Ideally, design the server so that air is drawn into the case over the drives, and exhausted out of the back/top. Additional fans may be required if the server is to be located in a cupboard/closet with minimal airflow. In some cases, an exhaust vent out of the cupboard/closet is necessary as well.

Monitor the drive temperatures to ensure that they remain in optimal ranges. Drive temperatures between 30 and 39 C are ideal, between 40 and 45 C are acceptable. Drive temperatures over 45 C are in the dangerous range. Many hard drives will shut themselves down if they get above 55 C.


Cabling

Good quality SATA cables are recommended; cheap cables have been known to cause problems. Locking SATA cables are also recommended, as non-locking cables are more easily dislodged due to drive vibration and, more commonly, user clumsiness.


Flash drive

Check that the USB Flash drive is supported. 1 - 2 GB is perfectly sufficient, though you may use a larger flash drive if you wish.


Monitor and keyboard

Although for the majority of its life an unRAID server does not need a monitor and keyboard attached, they are required for the first boot. This is to allow the motherboard BIOS to be examined, ensuring that attached components are detected and to enable the system to boot from the unRAID USB Flash drive (by setting an option such as 'Boot From USB-HDD'). In most cases there is no need to purchase a separate monitor and keyboard specifically for an unRAID server - you can just borrow a set from a desktop computer for the initial set up process. Some older motherboards don't support USB keyboards in BIOS. An unRAID server does not require a mouse at all.

NOTE: If using a KVM over IP enabled motherboard (such as IPMI), none of the above is required. You can simply log into the server from another system using your motherboard manufacturer's software to control the server remotely. This functionality includes control over BIOS settings and other non-OS related commands.