8 considerations before buying a NAS device

Considerations before buying a NAS device

Because of the costs involved, investing in a NAS device can be a daunting task. Here we discuss the considerations before buying a NAS device.


A network-attached storage (NAS) device is a stand-alone device, connected to a network, that typically has a large amount of storage space. Nowadays home NAS devices are hitting the upper thirty of Terabyte figures. NAS devices are in the form of multiple hard drives, managed as one large drive.

Stacked HDDs

A NAS is a device managing multiple hard drives as one. Image from startech.com.

Storage space

The most obvious factor to consider when buying a NAS device is storage space. More space is generally connected to more or more expensive hard drives.

Although the actual storage space is assumed to be a straightforward calculation, some RAID configurations with fewer hard drives will have relatively less usable space available — the rest will be occupied for redundancy (see later). The Synology website has a nice RAID space calculator.


Be prepared to pay a pretty price for a decent NAS device. Generally, the price is dictated by quality, amount of hard drive bays and commercial availability.

Aesthetics and orientation (see later) might also play a small part. In South Africa, an empty device (see below) is going to set you back at least a couple of grand. A proper, 4-bay NAS with hard drives will set you back at least ten. At the time of writing, anything below R 1000 per terabyte is a good deal.

0 TB or xx TB

Many NAS devices are marked as 0 TB. This actually means that only the NAS device (shell and CPU) is for sale, and does not include any hard drive(s).

For those that have a few hard drives lying around at home, those can be used instead. Devices without hard drives might, or might not be cheaper than those with hard drives.

Extra HDDs

Similar-sized hard drives can be used in NAS devices. Image from blogs.voanews.com.

When this is the plan, it is important to note that hard drives need to be the correct physical size (3.5 in vs 2.5 in drives — NAS dependent), the correct minimum amount of drives are available (see later) and that all the drives are compatible with the specific NAS device. It is also better if the hard drives have the same amount of storage space.

With two or more hard drives, some RAID configurations will start to be an option (see below). Adding hard drives to a NAS system with a RAID configuration will need reformatting. Using a RAID configuration will also format different sized hard drives to the capacity of the lowest drive (i.e. using a 1 TB and a 2 TB hard drive together will be formatted to give about 2 TB of space and not 3 TB).

Seagate BlackArmor NAS

The Seagate BlackArmor NAS device was available without hard drives and needed at least one hard drive to start off with.

In the case where a NAS system is already containing hard drives, one can likely rest assured that the hard drives are better suited for their specific device.

Hard drives that are used by NAS device manufacturers are considered for their speed and their reliability. Many hard drives are NAS optimised and are more suited for long working hours.

NAS devices that include hard drives are also generally sold at full capacity. There will be no additional bay slots to add more hard drives. If a RAID configuration is used, it might be a good idea to get at least one additional hard drive in case one of the drives fail.

Shopping around months to years later, might waste valuable time or be fruitless with regard to a similar size, brand or type of hard drive.

To RAID or not to RAID

RAID (redundant array of independent disks) is a way of storing the same data in different places on multiple hard drives. This is to protect data in the case of a drive failure. However, not all RAID configurationsĀ provide redundancy.

RAID 5 configuration

Visual representation of a RAID 5 configuration using 4 hard drives.

The RAID configuration used will be dependent on the needs of the network (not all data are equally valuable), the hardware capabilities of the NAS device and the number of hard drives available.

With a proper RAID configuration, it is possible to lose the functionality of at least an entire hard drive without losing its data. In the case of a defective hard drive, it can simply be swabbed out with a new one and the system will continue to function. The more important RAID configurations can be summarised as follows:


  • Store data continuously (SPAN) or striped (RAID 0) over all the hard drives
  • Need 1 (SPAN), 2 (RAID 0), or more hard drives
  • With these RAID configurations, one can start with one hard drive and, over time, add more drives without having to reformat the system
  • Use the maximum available space
  • This configuration will not allow any redundancy. If one drive packs up, that drive’s data might be lost.

RAID 1/10

  • Store data equally on 2 (RAID 1) or 4 (RAID 10) hard drives
  • Best redundancy. If one (RAID 1) and up to two (RAID 10) drives fail, they can be replaced and the system will redistribute the data back onto the empty drive(s)
  • With these configurations, you can only use about 50% of the total amount of space

RAID 6 (similar, but slightly better than RAID 5)

  • Stores a part of the total volume distributed over the total amount of hard drives
  • Some systems allow adding additional hard drives without having to reformat
  • Need 3 (RAID 5), 4 (RAID 6), or more hard drives
  • Good redundancy as you can still replace 1 (RAID 5) or 2 (RAID 6) drives without losing any data
  • One will lose the amount of space of about one of the total amount of hard drives

Number of hard drives

With 1 hard drive, only SPAN can be used. More hard drives can be added as time goes by.

With 2 hard drives RAID 0 orĀ  RAID 1 can be used. More hard drives can be added with some NAS devices when using RAID 0.

With 3 hard drives RAID 5 can be used. More hard drives can be added with some NAS devices.

With 4 hard drives RAID 6 or RAID 10 can be used. More hard drives can be added when using RAID 6.

NAS Backups

Many people forget that, like any electronic device, a NAS device can break. A NAS device can be divided into two major parts:

  1. the device itself
  2. the hard drives

The idea of configuring the hard drives using RAID is to have some redundancy on the hard drive. If one of the drives fails, the data can still be retrieved by replacing the failed drive.

Although unlikely, all the hard drives can fail at the same time. More likely is that the NAS device itself fails or it gest stolen. In South Africa for example, something like lighting surges and load shedding can cause device damage while all the drives are still perfectly intact.

In this case, all the data on the hard drives need to be transferred before the hard drives can be transferred to a different device.

Cloud backup services

Some NAS devices now come with easy-to-use cloud backup solutions integrated into their software. Data can also be saved on the cloud using third-party solutions such as Google Drive or AWS’ S3 solutions.

This makes it clear that NAS devices also need to be backed up from time to time.

Nowadays there are cloud backup solutions, but they become expensive with larger amounts of data. DVD backups are probably even less practical.

A practical solution would be to save valuable data on ‘the cloud’ and spend less time and effort on less valuable data.


NAS devices range from rough-looking, open rack systems to more aesthetic looking boxes. The orientation of the device might also be important to consider.

To make the device a little cheaper, the exterior of the device will often be neglected to focus more on the hardware and drives. On the other hand, some NAS device manufacturers also focus on the display of the unit.

The enclosure of the Western Digital’s My Cloud series is in the form of an upright book. These units are neat to display on a shelve and fits in nicely with, for example, their My Book external hard drive enclosure series.

Horisontal NAS device

An example of a horizontal rack-mountable NAS device. Image from albates.com.

While some NAS devices stack the hard drives on top of each other, horizontal units are also available. Horizontal units can, for example, easily slip into flatter spaces or can even be mounted in a drawer or under a shelve or a table.

LAN speed

Something to consider before buying a NAS system is the speed of the local area network (LAN) it will be connected to. Newer NAS systems have Gigabit Ethernet connectivity for fast data transfers.

To make use of speeds of up to 100 Mbps the Local Network Connection needs to be compatible.


The last consideration, especially in South Africa, is the manufacturer’s and/or the product’s reputation. When buying online, make sure its reviews are favourable. If no reviews are available locally, sneak previews from, for example, YouTube, Amazon or other larger online shops.


Here we discussed the considerations before buying a NAS device. They are storage space, cost, inclusion/exclusion of HDDs, RAID configuration, aesthetics, network speed and reputation.

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