A NAS exists in numerous sizes, with space for many or few drives, equipped with a variety of connections and powered with everything from lightweight ARM processors to server chips from AMD or Intel. How do you pick the right model?
Those looking for a NAS(Network Attached Storage) have many considerations to make. A NAS is much more than a hard drive with a network connection. The devices today take the form of servers that can support small teams or businesses with storage and backup but also with virtualization and applications.
To choose the right NAS, you need to know what specifications are relevant to your intended workloads. Do you want a basic backup solution? Or a central server for your SME? Does the device need to be expandable? How important is speed? We list the most important specifications to help ypu along.
1. Bays for the HDDs.
A NAS is defined in part by the number of drives you can fit in it. A 2-bay appliance with room for two drives is usually the minimum, although rare NAS appliances exist with room for only one hard drive.
A slightly more spacious device will have room for four or five drives. If you really need a lot of storage capacity, there are models with eight bays and more.
Keep in mind that the hard drives in a NAS are usually placed in a RAID configuration. That implies that data can be reconstructed if one drive fails, but also that you have to consider a higher disk capacity than what you need at first glance.
Two bays are good for modest use, yet four or five is quickly becoming the norm for those who want to manage larger amounts of data in a professional context. If you fill a 5 bay NAS with 6 TB writes in RAID 5, you still have 24 TB of capacity available. Even more bays are possible. These large devices become interesting for larger teams, or users who generate very large amounts of data. Think videographers, for example.
You pick the amount of bays taking into account the amount of storage you think you need, and the drives you want to put in them. You can go for some immense 20 TB drives, but then you lose a lot of time (and money) when one breaks down. Smaller drives spread across multiple bays are often more interesting. Although there is no easy to follow rule, we suggest the following guideline:
- 2-bay with drives up to 4 TB, in RAID-1, for 4 TB of maximum space. Convenient for modest use.
- 4- to 6 bay with drives up to 8 TB in RAID-5, for 30 TB maximum space
- More bays in case you need more space than 30 TB. In that case, you can also choose larger drives.
The choice of 8 TB as a preffered mixumum is motivated by the recovery time of a drive in a RAID-5 configuration: larger drives take a very long time to recover.
2. Rack or shelf
A classic NAS is a desktop tower device. The devices sit like a mini-computer on a cabinet or shelf. That’s handy for small offices or home situations. Large and heavier NAS appliances are also popular with SMEs with a little more IT infrastructure.
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For that scenario, NAS devices also exist in server form, ready for rack mounting. That’s an added value for those with rack space available. The form factor says nothing though about the performance or capacity of a NAS.
- A rack is useful for companies that already have one in place, such as for another server, switch or firewall.
- A desktop model is fine when no rack is available. You can put it on a shelf or in a (ventilated) cabinet.
3. Flash and cache
A NAS is traditionally designed to house 3.5-inch HDDs via a SATA connection. Smaller SATA SSDs usually fit as well. However, some devices are built with flash storage in mind. They only provide space for SSDs.
That can be useful for use cases where storage needs to be accessible super fast. Think of a NAS that will house a database, or another device from which video editors want to wprk with 4K video directly.
Other NAS devices have space for one or more M.2 connections. An M.2-NVMe SSD can serve as additional storage, or as a cache to speed up access to the NAS. For example, you can run some containers on the flash storage, but keep the data on the HDDs.
- All-flash is useful for specific purposes, such as video editing or powerful databases.
- Flash cache or a modest flash volume can add value to speed up the use of your NAS.
- For ordinary backups or use as a network folder, flash is irrelevant.
4. Connections
How often do you transfer data to and from the NAS, and how fast should it be? 2.5 GbE connections are gradually becoming the norm. Qnap offers them on all devices, other manufacturers are (partially) following suit. 2.5 GbE is sufficient to quickly move data to and from a network folder, or to make backups.
If you are using a NAS with a larger team, and the appliance needs to handle larger volumes of data, then a 10 GbE connection becomes more relevant. Some NAS appliances already have such a connection on board, but it’s not standard. For truly professional purposes, you can go for 25 GbE or faster, though then aim for niche workloads.
- 1 GbE is sufficient for a small 2-bay NAS, but is gradually becoming dated.
- 2.5 GbE is sufficiently fast for ordinary use.
- Intensive use with multiple people can justify 10 GbE or more.
5. The right CPU
If you want a NAS for backing up a few computers, you don’t need a lot of processing power. A light processor can handle such a task just fine. For such usage scenarios, manufacturers market NAS appliances with light ARM processors. These also consume very little, which is a good thing since a NAS is built to be permanently on.
If you want to use a NAS for multimedia capabilities or video surveillance, it’s best to make sure you have a suitable CPU that supports media hardware-wise. A built-in NPU for AI-related tasks such as image recognition can also be useful.
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However, NAS manufacturers are increasingly assuming that customers want to run more sophisticated tasks directly on the NAS. Think media server, containers or even virtual machines. In such cases, you need a more capable processor. Copies from AMD or Intel are then more interesting. After all, the x86 architecture provides broader compatibility. The same goes for available apps within the ecosystem.
Are containers or virtual machines really a main goal, and do you want multiple users to be able to smoothly run applications on your NAS? Then you may consider a true server processor such as an Intel Xeon chip or an AMD Epyc CPU.
- For light use as a network folder or for backup, you can choose a light and economical processor. This could certainly be an ARM chip.
- If you want to use more applications, an x86 chip provides a wider ecosystem. That may be a light Intel Celeron or AMD Embedded. That will get you a long way.
- To run single containers or multiple applications consistently simultaneously, a more powerful chip from Intel or AMD is useful.
- Only for heavy use with multiple containers and virtual machines, and many users, are server chips such as an AMD Epyc or Intel Xeon important. These are less economical, so select them only when necessary.
- Are media or surveillance important? Then make sure the CPU supports media tasks hardware-wise and possibly has an NPU on board. This is more relevant than pure CPU computing power.
6. RAM
The amount of RAM present is especially important in scenarios where the NAS also serves virtualization, or for users who want to take full advantage of the app ecosystem. 4 GB is enough for basic use such as backups and shared storage. 8 GB goes a long way when the focus is on applications from the NAS ecosystem. More becomes relevant with more advanced applications including virtualization.
NAS manufacturers are usually sparse with the amount of RAM they put in their devices, aiming more for basic use. Almost always, though, the RAM is expandable. So you can feel free to install more RAM when you hit a wall.
- Network storage does not need a lot of RAM. 4 GB is enough for light use.
- With 8 GB, you can already run a lot of apps or containers.
- More than 8 GB is relevant when containers and virtual machines are of great importance.
7. Expandability and connections.
External expandability is a final important point to judge the NAS on. Many devices have one or more USB (A) ports on board. These can serve to connect external drives, but also, for example, to allow a UPS to communicate with the NAS.
Several RJ-45 ports, in turn, allow the NAS to be connected to redundant networks. Many slightly larger NAS appliances, especially from four bays or more, have space for a PCIe card. With this, you can add additional M.2 SSD capacity, for example, or network connections up to and including 100 GbE.
Finally, you can also expand an entire NAS. If four bays prove insufficient, you can purchase a device with additional bays. You connect that via cable (and possible PCIe connection) to your NAS. Such an expansion bay is cheaper than a new NAS, and has no extra CPU or RAM on board.
- If you want great future-proofing, make sure you can connect an expansion unit with additional bays.
- PCIe allows you to install additional network functionality or an SSD.
What is your NAS used for?
As you can see, there are a lot of options. Concider carefully the purpose of your NAS, so you know how capable the CPU needs to be and how relevant RAM is. Before picking the number of bays, try to imagine how quickly your storage needs wil increase over the years, and remember that a solution with more bays with smaller drives is often more interesting and robust.
Lastly, the software matters as well. A simple NAS doesn’t need to have many capabilities, but for advanced use, the OS and ecosystem are very relevant. These determine what additional functionality you can exploit, as well as how easily you can manage multiple users.