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Data storage for everything: A NAS is suitable for backups, music, films and much more
Photo: Andreas Martini
The abbreviation NAS stands for Network Attached Storage, i.e. mass storage with network connection, sometimes also called a network hard drive.
The NAS boxes for self-equipping with hard drives, which are sold at prices starting at around 100 euros, can do much more than just store data and provide this service for all devices in the local network.
Because their firmware, maintained by the respective manufacturer - which almost always means a tailor-made operating system with a Linux core - has a wealth of built-in functions and can be easily expanded with plug-ins.
NAS boxes then also work as media servers for photos, videos and music, serve as a local backup target and bring cloud functions into your own home.
You no longer have to hand over confidential data to more or less trustworthy cloud service providers.
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NAS boxes can easily be equipped with hard drives, usually without tools
Photo: Melissa Ramson & Andreas Wodrich / c't
The range of NAS boxes is huge, with the market leaders Synology and Qnap alone offering over 100 devices in stores.
In this buying guide, we focus on inexpensive network storage with two drive bays, also known as 2-bay NAS.
They offer sufficient capacity for the typical home office and, if desired, protection against hard drive failures.
Many are quiet and economical, so they do not disturb your work.
If you need more space, but no further functions, the technology of the affordable devices can also be found in NAS for up to four disks.
NAS or not?
A central network storage can also be set up without a NAS box, for example with a Raspberry Pi or with the NAS functions of an already existing (WLAN) router.
However, both approaches have considerable limitations.
A Raspi NAS is only suitable for people with sufficient knowledge of Linux and hardware.
A router NAS offers only a fraction of the functions of typical NAS boxes and usually much less performance.
Above all, however, you have to connect an external USB disk to the router NAS, which leads to operating errors: If you accidentally disconnect the USB cable while someone is still writing to the disk via the network, there is a risk of data loss.
These approaches are only suitable for simple applications, for example to provide copies of media files that are securely stored elsewhere for network access.
Almost every PC can also be converted into a NAS, for example by setting up file shares under Windows or Linux or installing NAS software such as TrueNAS or OpenMediaVault.
Many older PCs, however, swallow an unnecessarily large amount of electricity or rustle loudly when in continuous operation, and with a newly purchased mini PC the NAS becomes more expensive than a finished box.
The disadvantages of the alternatives demonstrate the advantages of finished NAS boxes: The latter protect hard drives mechanically and cool them quietly with a temperature-controlled fan.
Years of experience flow into the NAS hardware of the established brands, and the manufacturers maintain compatibility lists for hard drives, which reduces the risk of breakdowns.
You get a complete device from series production including support, documentation and with predictable power consumption.
Above all, the NAS firmware, which has been optimized over several generations, makes setting up network storage much easier and reduces the risk of fatal operating errors.
The big manufacturers also deliver updates that close security gaps - but this does not apply to every plug-in installed at a later date.
For a safe and reliable NAS configuration, however, some basic knowledge is required, above all you should deal with the concepts of user management and access rights.
We will provide detailed information on the secure NAS configuration in one of the upcoming "c't" issues.
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For use in the home office, a NAS needs Gigabit Ethernet and USB 3.0 (right);
A second Ethernet port is just as dispensable as an eSATA socket (left, red) for expansion
Photo: Melissa Ramson & Andreas Wodrich / c't
NAS functions
Each NAS manufacturer maintains its own firmware ecosystem, an article on page 26 of the "c't" magazine 1/2021 goes into more detail.
The basic functions are the same, because it is ultimately about so-called file servers.
There is also an economical processor in the NAS box, on which an adapted Linux runs.
The latter integrates the hard drive, USB and network interfaces, manages the storage space of the built-in data carriers and the rights of the users who should have access to them.
A NAS normally works without a screen, keyboard and mouse; it is configured from a computer using a browser.
There you usually set up so-called file shares, to which certain users (groups) then have access - and others do not (data protection).
Each NAS enables data access using the Windows Server Message Block (SMB) share protocol, formerly known as the Common Internet File System (CIFS).
Windows computers can use an SMB share as a backup target, which is one of the most important functions for the home office.
Practically every current PC can handle SMB, whether with Windows, Linux or Apple's macOS;
There are also suitable apps for smartphones and tablets with Android or iOS.
All NAS support other network protocols, for example to connect Apple computers with the Time Machine backup function or for WebDAV shares.
Media server functions are also common: they make video, music and image files available in the network so that they can be played on smart TVs with UPnP functions, for example.
With plug-ins from the online store of the respective NAS provider, many other server functions can be retrofitted, such as smart back-up services or cloud replacement functions such as NextCloud.
However, the latter only make sense for most users if they also work outside of their own network, i.e. when they are on the move - and this is where things get complicated: If you make your NAS accessible from the Internet via port forwarding and DynDNS service, you can easily open security gaps .
For a domestic cloud replacement, it is better to use a VPN connection to the home network.
RAID
Hard drives are now available with a capacity of up to 18 terabytes (TB), which is sufficient for the vast majority of home offices.
You can also operate a single disk in the 2-bay NAS: This saves money and electricity and is often sufficient if you have really regular backups.
Because hard drives can fail at any time like any other hardware, it is wiser to use a second hard drive in the NAS for a redundant network of two drives, a so-called RAID 1. The NAS writes all data to both drives at the same time;
if one fails, no data is lost.
However, a RAID is no substitute for a backup because it neither protects against accidental deletion nor against encryption Trojans or the failure of the NAS hardware.
A NAS is a good backup target for PCs, but there should always be at least one additional copy on another storage medium that is not constantly connected to the network and, if possible, not stored in the same location - i.e. on a USB disk or encrypted in the cloud.
Some NAS do the latter automatically via a plug-in.
It is
downright reckless
to couple two NAS disks to form a faster and larger, but also more error-prone RAID 0 array - then a single
disk defect destroys
all
data because it is distributed in strips across both disks (striped set).
Problems also threaten with the so-called JBOD, which combines the added space of both disks into a single logical volume.
If space is tight, it is better to retrofit a larger disc.
speed
Current 100 Euro NAS have Gigabit Ethernet (GE) sockets that transfer up to 115 megabytes of data per second (MB / s).
A single modern disk can do even more in its fastest zones and is therefore sufficient to copy large files as quickly as possible.
If the NAS achieves 100 MB / s, the transfer of a backup file or a DVD image of 4 GB each takes less than 50 seconds.
When accessing many small files, the transfer rate drops enormously - but this can only be optimized to a certain extent and even that is expensive because you need a NAS with a lot of RAM and SSD equipment.
This is just as rarely worthwhile for small offices as a faster Ethernet connection with 2.5 gigabits per second (Gbit / s) or even 10 Gbit / s.
Because in order to exhaust that, you also need a fast switch and the right connections on the PC.
If you use your NAS primarily via WLAN, you can only use the full transfer rate even with Wi-Fi 6 if the notebook is close to the WLAN router.
The WLAN transfer rate drops rapidly with increasing distance.
In other words: If the notebook usually has a weak WLAN connection, you don't need a fast NAS.
If you have to transfer large files very often, it is better to use an Ethernet cable.
For notebooks without Ethernet there are corresponding USB adapters from around 15 euros;
you need a USB 3.0 port, USB 2.0 is too slow for that.
Although most NAS processors have AES accelerators for encrypting data when writing to the disks, the transfer rate can drop significantly.
You have to weigh up how much it bothers you.
If you want to store customer data on the NAS, you should activate encryption for at least one share reserved for it - data can easily get into the wrong hands, for example when the device is sent in for repair.
For backing up to an external hard drive, the NAS should have a USB 3.0 socket (also known as USB 3.2 Gen 1);
this is now the case even with inexpensive devices.
NAS hard drives
There is no general answer to how much storage space a NAS should have, because it depends on your individual wishes.
As a back-up goal for the home office, you don't need much more than double to triple the capacity of the SSDs and disks of your own computer.
Don't buy extremely oversized drives, not only because they are expensive, but also because they won't last forever.
It makes more sense to plan a move to larger and then fresh records after three to four years.
The old ones can then be stored as an additional backup.
Almost all hard disks can be used in the NAS;
Most of them even fit the more economical and quieter 2.5-inch drives for notebooks.
However, it is advisable to stick to the compatibility lists of the NAS manufacturer when making your selection and to use disks that are specially designed for NAS operation.
All three remaining hard drive manufacturers Seagate, Toshiba and Western Digital (WD) offer special drive families for small NAS.
Their properties (and prices) are somewhere between those for desktop PCs and those for large NAS and "Enterprise" servers.
Unlike desktop types, the NAS versions are designed for continuous operation, tolerate vibrations from other plates in the same system better and work relatively economically.
However, they rotate more slowly than the faster types for larger servers, do not actively compensate for vibrations and are designed for lower annual data transfer volumes.
The latter should not be decisive in the home office.
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The three major hard drive manufacturers sell drives specifically for small NAS;
pay attention to a model with conventional recording, i.e. without SMR technology as with this WD Red
Photo: Melissa Ramson & Andreas Wodrich / c't
A well-known series of drives for small NAS is the WD Red, which is now called WD Red Plus.
However, in mid-2020, WD annoyed some buyers with confusing data: For example, they tacitly delivered WD Red records with the recording technology Shingled Magnetic Recording (SMR), which can lead to problems in some constellations.
Conventional Magnetic Recording (CMR) is better for small NAS - and this is exactly the technology that is in the WD Red Plus.
In addition, WD sold records of the "5400 tour class", the magnetic discs of which actually rotate 7200 times per minute and swallow a little more electricity.
The Toshiba series, which is comparable to the WD Red Plus, is simply called »NAS Drive«, Seagate recommends the »Ironwolf« series.
The 4 TB models of the disk families mentioned cost from 90 euros, 2 and 3 TB models are only slightly cheaper and are therefore no longer worthwhile.
For NAS disks with 6 and 8 TB you pay a similar amount per terabyte as with the 4 TB types, from 10 TB it becomes more expensive.
Disks from 8 TB, which work somewhat more economically with the same capacity and speed, are also available with helium filling.
A NAS is usually left running all the time, most of them automatically switch off their disks after a while without access.
Simple NAS use around 5 to 15 watts of power when idle with upright disks.
At an electricity price of 30 cents per kilowatt hour, that adds up to 13 to 40 euros per year.
When accessing the NAS processor needs more power and each disk between 4 and 8 watts, consequently between 13 and 31 watts in this example.
Because a NAS in the home office seldom transmits data for more than four hours on 230 working days per year, only 4 to 9 euros are added, so the total is 17 to 48 euros.
If the records were constantly rotating, it would instead be between 34 and 103 euros.
The right location
Hard drives do not tolerate shock and heat well.
Dust, dirt, moisture (basement, kitchen) and vibrations from other devices (printers) can also cause NAS problems.
In the home office, a NAS should also be out of the reach of children and pets.
If there are frequent disruptions in the power grid at your place of residence, an uninterruptible power supply (UPS) protects against hardware defects and the resulting data loss.
Think about regular backups and data protection, especially if you process data from customers and colleagues (GDPR).
Encryption helps here.
A test of several NAS systems as well as an examination of the various NAS operating systems
can be found in »c't« 1/2021
.
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