One of the great unsung features of the macOS is Time Machine, the software that sits inside your System Preferences panel and quietly performs an automatic backup of the entire contents of your Mac's hard disk every hour, on the hour.

If you accidentally delete a file you can just go back and check out all the previous versions of that file that you backed up in the past. And if your Mac starts behaving oddly and you think you might have been infected by some sort of virus or malware then you can just reboot your Mac and use Time Machine to restore the entire macOS to an earlier, untarnished state.

But, of course, in order to use Time Machine you do need to have an external hard drive connected to your Mac that can store all your old backup files. Hard drives are pretty cheap these days, but as we all start to own more and more desktop computers, laptops and mobile devices, it starts to become both expensive and rather impractical to buy a separate backup drive for every single device in our home or office.

The answer to this problem is a NAS drive.

What are the advantages of a NAS drive?

Rather than connecting your hard drive to a USB or Thunderbolt port on a single Mac, a NAS drive (NAS standing for network-attached storage) can be connected to an Ethernet port on the network router in your home or office network, and the storage space on the drive can then be shared by everyone that has access to your network. (Here's how to set up a NAS drive.)

Early NAS drives were expensive and complicated, and were mostly used by large organisations that needed a central back-up device that could be used by multiple employees. But most homes these days now have their own Wi-Fi networks, which are shared by several people who often own multiple devices. This means that a shared NAS drive now makes sense for many home users as well.

NAS drive features to look for

Time Machine support

Most NAS drives are 'Mac-compatible' - but not all of them are what we might call 'Mac-friendly'. For instance, not all NAS drives will allow you to use Time Machine to make backups over the network, so support for Time Machine is a key feature that you should check on when thinking about buying a NAS drive for use with one or more Macs.

User accounts & sharing

Another important feature is the ability to create individual user accounts, so that each person in your home or office can have their own private area on the NAS drive for storing their personal files. And, at the same time, it's also handy to create 'shares', which are like public folders that can be shared by everyone - perhaps for storing music or photos for the whole family.

Most NAS drives will allow you to do this, but sometimes you need a bit of network know-how to figure out how each drive handles this process (and some drives, such as Apple's own Time Capsule, just ignore this side of things altogether and simply focus on the basic task of handling Time Machine back-ups).

Mobile device support

And, of course, you'll also want to check that your new NAS drive provides an iOS app for your iPhone or iPad. Most of us now tend to use iCloud for backing up photos, videos and other files from our iOS devices, but it can give you extra peace of mind to know that you've got a spare backup on your NAS drive in case anything goes wrong.

A good NAS drive will also let you share your photos and videos with other people by streaming them to mobile devices over your network, or possibly even provide a remote access option that allows you to retrieve files over the internet when you're away from home (a feature that manufacturers often refer to as a 'personal cloud').

File streaming

Many people also use their NAS drive as a kind of central media server for their home, perhaps streaming music and videos to a games console that is connected to their TV in the front room. Mac users should check to see if a NAS drive can stream files to an Apple TV, or act as an 'iTunes server', storing your iTunes music library on the NAS drive so that it can stream music to every Mac or iOS device on the network.

How much storage do I need?

That's something you'll need to decide for yourself, but it's worth mentioning that some NAS drives are more flexible on this point than others.

Some of the less expensive NAS drives are sold with a built-in hard drive - generally at least 2TB - but the hard drive is fixed and can't be replaced once it's full (although the NAS drive may have a USB port that lets you connect a conventional USB hard drive in order to add some extra storage). This is the simplest option, favoured by most home users and small businesses, as it means you can just unpack the NAS drive and connect it to your router to get started.

The unpopulated option

However, many NAS drives are sold 'unpopulated' - without any internal hard drives already installed - and simply provide two or more empty drive bays into which you insert your own choice of hard drives. This option is more expensive, but it allows you to customise the NAS by buying your own hard in order to provide as much storage as you need. And, if you run out of storage space, you can just take out the old drives and insert new, larger drives in the future.

This type of NAS drive generally also offers a number of 'RAID' options - this stands for "redundant array of independent disks" - which use multiple hard drives to provide additional performance and data protection.

1. WD My Cloud Home

WD My Cloud Home

You're spoilt for choice when it comes to Western Digital's My Cloud range, with several models available for home users and small businesses, as well as a number of Expert and Pro models for larger organisations.

The original single-drive My Cloud is getting a bit old now, but it's still around and starts at just £125/$140 with 2TB of storage. However, you're probably better off getting the newer My Cloud Home model shown here, which is a little more expensive, but is faster and provides a few additional features, such as support for the Plex Media Server software (although that's probably not a must-have feature for Mac users).

The single-drive version of the My Cloud Home that we review here costs £145/$160 with 2TB of storage, going up to £290/$320 with 8TB, which should be more than enough for most homes, as well as small offices and self-employed users. The slimline white-and-silver unit is neatly designed, and only measures 2in wide, so it'll sit easily on your desk, or on a shelf close to your router without taking up too much space.

There's also a larger dual-drive model, called the My Cloud Home Duo, which houses two matching drives and costs up to £600/$700 with a pair of 8TB drives (for 16TB total). That provides RAID 1 mirroring for extra data protection, but if you want more sophisticated RAID features, as well as the ability to install and remove drives yourself, then you'll need to step up to the My Cloud Expert (from £144/$160) or My Cloud Pro (from £341/$400) models.

Western Digital always does a good job with Mac support, and the My Cloud Home is no exception, with apps that handle a range of tasks quickly and easily. The iOS app can perform automatic backups of your photos and videos, while the Mac app lets you use Time Machine for your backups (and there are Mac and Windows versions of the apps available too).

There are some nice touches too, such as the ability to right-click a folder on your Mac and automatically sync the contents of that folder onto the My Cloud Home. That will be handy for people who want an extra backup of their current work files or projects in addition to the basic Time Machine backup. You can also right-click any file that is stored on the My Cloud Home and send a download link in order to quickly share that file with friends or colleagues.

And, if you also use an online back-up service, such as Dropbox, then you can sync the contents of your Dropbox account onto the My Cloud Home too. You can even back up photos and albums from Facebook on to the drive for safekeeping if you want to.

There are a couple of rough edges, though. You can't simply double-click the drive's icon on the Mac desktop in order to open the drive and then drag-and-drop to copy folders or files onto the drive. For some reason you have to open the app's pulldown menu and view the contents of the drive through the app instead. You can't create individual user accounts on the Mac either, so you're forced to use the iOS app on an iPhone or iPad if you want to invite someone else to create their own personal folders on the My Cloud Home drive.

Most Mac users will have an iPhone or iPad, of course, but we'd like to see the Mac app updated to allow you full freedom to control the My Cloud Home with your Mac as well.

2. Drobo 5N2

Drobo 5N2

A five-bay drive such as the 5N2 might be unnecessary for home users, but Drobo has a well-deserved reputation amongst professional and creative users who need a versatile and reliable NAS drive.

The 5N2 is more expensive than most of its rivals - and the company doesn't currently make any less-expensive 2-bay models - costing around £430/$550 when bought 'unpopulated', so you still have to budget for your hard drives on top (although some online stores also sell packages that include the 5N2 with drives already installed). But while the nondescript black box isn't much to look at, the 5N2 will earn its keep in your office as it is absolutely packed with features designed to keep your data safe.

Drobo claims to offer "the benefits of RAID without the complexity", and the company does a really good job of helping newcomers to get started and showing you how to use the 5N2.

Even before you turn it on or install a single hard drive into the 5N2 you're instructed to go to the Start page on the Drobo website. This shows how you can simply slot the drives into the 5N2 and then connect it to your router - and the 5N2 even has two Gigabit Ethernet ports, which can be 'bonded' together to provide higher performance for devices such as the iMac Pro, with its 10GB Ethernet interface.

After the initial setup, you're prompted to download Drobo's Dashboard app for Macs and Windows PCs. This installs a pulldown menu into the main menu bar at the top of your Mac's screen, providing instant access to the drive's main features.

However, you probably won't need to use Dashboard very often, as many of the drive's features work automatically. Once the drives have been installed there's a series of lights on the front panel that indicate the status and health of each drive, along with a row of blue lights that act as a capacity gauge to let you know when you're running out of storage.

The 5N2 also allows you to 'hot-swap' drives, removing and replacing faulty drives, or simply adding some extra storage without having to restart the unit. It even has a small built-in battery that can protect the 5N2 from power failures, keeping it running long enough to complete the current task and then shut down without losing any data. And, rather than offering conventional RAID modes the 5N2 uses Drobo's own BeyondRaid software to automatically protect your data (which comes in handy if, like me, you can never remember the difference between RAID 0 and Raid 1).

In fact, most people will probably only use Dashboard to set up user accounts for other people who also need to use the 5N2 for network storage, or to set up Time Machine backups for your Macs - which you can do at the same time as setting up the 'share' for each user. If you want to explore further, then Dashboard also allows you to install additional apps, such as the Plex media server, or Drobo Access, which provides remote access over the internet. There are iOS and Android versions of Drobo Access available too, so that you can view and edit files stored on the 5N2 with your mobile devices, along with a DroboPix app that allows you to back up your photos and videos.

It's probably too expensive for most home users, but the admirable ease of use provided by the Drobo 5N2 makes it an ideal choice for small businesses and creative users who may not have used a NAS drive before. And, with failsafe features such as its internal battery, the 5N2 can offer rock-solid reliability for protecting your most important data.

3. Seagate Personal Cloud

Seagate Personal Cloud

Seagate used to make a two-bay version of the Personal Cloud that came with two drives already installed, and also allowed you to open the case and replace or upgrade the drives yourself. That model seems to have been discontinued, but this remaining fixed-capacity, single-drive model is still a good option for home users who need an affordable network storage device for backing up photos, videos and other files.

The single-drive model is available with 3TB, 4TB or 5TB of storage, costing around £150/$126, £175/$180 and £210 respectively. You can't replace the drive yourself - and it doesn't offer the RAID options that were available with the 2-bay model - but that should still be enough storage for most families, or even self-employed people who need a network drive for their work files. And, while the hardware design is fairly conventional, the Personal Cloud stands out thanks to a number of apps that are absolutely packed with useful features.

For basic backup and file access, there's a mobile backup app that is available for iOS and Android devices, along with a second app called Seagate Media that allows you to stream photos, videos or music from the Personal Cloud to your mobile devices. You also have the option of setting up a Seagate Access account that allows you to stream files remotely over the internet when you're away from home (but watch out for those mobile data charges when you're travelling). You can also use the Media app to connect to other cloud services, such as Dropbox, and if you get caught on the road without the required apps or devices then you can log into your Seagate Access account via a web browser on any computer or device that has internet access.

Macs and PCs have their own app for backups, called Dashboard. This works with Time Machine for automatic backups, but also provides additional options that might be handy for office users, such as the ability to schedule backups for specific times - perhaps at the end of the day after you've finished work.

There's a 'continuous backup' option, which watches for changes to any files while you're working and automatically makes backups on the spot whenever you edit or delete any files on your Mac. You can also plug a memory stick or hard drive into the USB port on the back of the Personal Cloud and back up files from those external devices too.

As well as Macs, PCs, and mobile devices, the Personal Cloud is compatible with an impressively wide range of other devices too. You can stream video to an Apple TV, or rival media players such as Google Chromecast and Roku. It's compatible with a number of smart TVs from LG and Samsung, and supports the DLNA networking system used by games consoles such as the Xbox and Playstation.

Only minor complaint is that all these features are spread across a variety of apps that might be a little confusing when you're first getting started, and Seagate's online manual has an annoying habit of simply listing features without always making it clear where you can find them or how to use them. That slightly untidy approach means that it might take a little while to get the Personal Cloud set up just the way you want it, and more experienced users might prefer a NAS drive with accessible drive bays that provide greater upgrade potential.

But if you're looking for a versatile NAS drive that offers plenty of storage at a competitive price, the Personal Cloud is hard to beat.

4. Netgear ReadyNAS RN212

Netgear ReadyNAS RN212

Netgear's ReadyNAS 212 has been around for a while, and it's showing its age a little, but its combination of strong data protection and good Mac support ensure that it will appeal to both home and small business users alike.

The hardware design is a little old-fashioned, consisting of a simple black box with two drive bays for adding storage. The RN212 costs about £240/$250 when bought on its own without drives, but Amazon and some other dealers sell packages that include drives as well, so you should shop around to see what's on offer.

Along with the drives that you choose to install, the ReadyNAS provides some useful features for adding extra storage and enhancing performance.

There are no less than three USB 3.0 ports for connecting USB storage devices - one on the front and two on the back - and even an eSATA interface for high-performance storage systems. The ReadyNAS also includes two Gigabit Ethernet ports, which can be used together to connect to the superfast 10GB Ethernet on the iMac Pro.

Installing the internal drives is a little fiddly, though. The trays that hold the two drives pop out of the front of the unit easily enough when you press down on a small latch, but the next step is a little confusing as it involves slotting the hard disk drives into a flimsy plastic bracket that then has to be lined up in just the right position before you can push the trays back into the enclosure. It took us a couple of attempts to get it right but, thankfully, once that's done Netgear's ReadyCloud software takes over and setting up the drive on your network proves to be very straightforward.

Once you've connected the ReadyNAS to mains power and then to your router, you simply launch your web browser and go to the web page for Netgear's ReadyCloud service. This web page automatically detects the ReadyNAS on your network, and can also check for any problems if the drive isn't working properly.

There are two options for getting started, with simple 'offline' installation allowing you to quickly connect the ReadyNAS to your network and start backing up your files - including using the drive for Time Machine backups on your Macs. The other option is to create a ReadyCloud account, which provides remote access over the internet as well, so that you can connect to the ReadyNAS and retrieve files even when you're away from home.

You also use your web browser to manage the ReadyNAS, but we were pleased to see that the various settings are well organised and easy to use. All the key features are organised under simple headings, such as Shares for creating individual user accounts, or Cloud for setting up remote access or syncing with other cloud services such as Dropbox or Microsoft Azure for business users.

There's good support for Mac technologies too, with options for 'shared' Time Machine backups, which store the backups for multiple Macs in one folder on the ReadyNAS, or 'private' backups for individual users that are all kept separate. You can even specify the amount of storage space that is allocated to individual Time Machine backups so that no one person can hog all the storage for themselves.

The ReadyNAS can act as an iTunes server for storing a central iTunes library, and also supports the Plex media server and DLNA for streaming to devices such as games consoles. It can handle a spot of video transcoding, too; this is limited to 1080p (HD) video, reflecting the age of the RN212, but that should still be fine for most people. And, of course, there's a ReadyCloud app for iOS devices too, which allows you to back up photos and videos from your iPhone or iPad, as well as streaming files that are stored on the drive.

5. Synology DiskStation DS218

Synology DiskStation DS218

Synology is best known for its high-end network and storage systems for business users, but it does have a 'value' range for home users and small businesses. The £245/$250 two-bay DiskStation DS218 is the successor to the DS216 that has impressed us in the past.

The DS218 makes a good first impression. It's sold 'unpopulated', which means it is up to you to buy and install the drives you want, but Synology makes it easy to get started. There are no nuts, bolts or screws to worry about, as the empty drive bays include two trays that pop out with the press of a button. We were able to insert our drives into the trays with no trouble at all, and get started in a matter of minutes.

There's one Gigabit Ethernet port on the back for connecting the DS218 to your router, and three USB ports - one on the front, and two on the back - that can be used to plug in a memory stick, camera or external hard drive so you can transfer files on to the DS218. The USB port on the front even has a 'Copy' button just beneath, which can be used to automatically back up any files on your storage devices on to the DS218. The only oddity here is that the front port is USB 2.0, while the two ports on the back use the faster USB 3.0.

Once you've inserted the hard drives and connected the DS218 to your router, you can simply type find.synology.com into your web browser and this will take you to Synology's online Web Assistant. The Assistant magically detects the DS218 on your network, and installs Synology's DiskStation Manager (DSM) software for you.

But this is where things start to get a bit more complicated. The DS218 is certainly packed with useful features - it can be used for Time Machine backups, and there are RAID 0 and RAID 1 options for enhancing performance and security, along with Synology's own 'hybrid' RAID format that allows you to combine disks of different sizes within the DS218. There's also a QuickConnect option that allows you to connect to the DS218 over the internet when you're away from home.

The DS218 works well as a media server too, with a powerful 1.4GHz quad-core processor that allows it to convert (transcode) video files into various formats suitable for a wide range of different devices - it can even handle 4K video for streaming to an Apple TV or other media player. There's an iTunes Server option that lets you store a central iTunes library on the DS218, and it can stream music to AirPlay speakers too.

The only problem here is that the web browser interface used by the DSM software to control all these features on the Mac is pretty complicated.

Different sets of features, such as those for working with music or video are handled by a collection of 'packages', which are like mini-apps that you need to install from within the DSM browser interface. There's a lot of technical jargon thrown around, and new users may well feel overwhelmed at this point.

The mobile side of things is complicated too - with around a dozen different apps available for your iOS devices. These do provide useful features, such as the ability to back up photos from your iPhone on the move, and there are even apps for the Apple TV and Apple Watch. However, getting to grips with so many different apps and features will be a daunting task for most people.

Synology does provide extensive help files and tutorials on its website, and hobbyists who like to delve into the fine details of NAS drives and media servers will really appreciate the depth and scope of the DS218. However, it's a serious case of overkill for home and small-business users who are simply looking for a straightforward NAS for their Time Machine backups.

6. Apple Time Capsule

Apple Time Capsule

Apple's Time Capsule is actually a bit of a weird device. It comes with a typical Apple price tag that makes it quite a bit more expensive than most of its NAS rivals, costing £299/$299 for a model with 2TB of storage or £399/$399 with 3TB. However, the Time Capsule also differs from a conventional NAS drive in a number of ways, and it might well be the ideal plug-and-play back-up solution for some Mac users, while being over-priced and too inflexible for others. And, if you're lucky, you can sometimes find refurbished Time Capsule models for sale on the Apple Store with discounts of up to 30%.

The Apple-esque design is typically distinctive. Rather than the boring 'black box' design adopted by most NAS drives, the Time Capsule consists of a gleaming white tower that stands almost 7in high. It's virtually identical to Apple's AirPort Extreme Wi-Fi router - and that's because the Time Capsule actually houses both an internal hard drive for storage, and a built-in AirPort router that also provides 802.11ac networking. If you're still using an older 802.11n router then the Time Capsule can help to justify its high price by giving you a faster, more reliable wifi network (although you'll still need to hang on to your existing router, as the Time Capsule will need to connect to that in order to get internet access).

Setting up the Time Capsule is also very simple and straightforward for Mac users, as Apple's AirPort software is built into the macOS on all Macs and can automatically detect the Time Capsule and guide you through the installation process. Some NAS drives can be really confusing for first-time users, so the simplicity of the Time Capsule is its main strength for home users or small businesses that don't have their own IT staff. And, of course, the Time Capsule works with Time Machine as well, allowing you to easily back up multiple Macs over the network using either Wi-Fi or wired Ethernet connections.

Tucked around the back of the Time Capsule there are no less than four Ethernet ports - one for connecting to your existing router, and three for wired connections, which will be useful for offices or home workers who prefer to use a wired network. There's also a USB 2.0 port, which allows you to add extra storage or a printer that can be shared on the network. People using Windows PCs can connect to a hard drive or printer connected to the Time Capsule network, but the Windows version of the AirPort software hasn't been updated for a while so the Time Capsule is really best suited for homes or small businesses that are primarily Mac-based. And, with just a single, non-replaceable hard drive, you can't upgrade the internal storage at all, or configure the Time Capsule as a RAID drive.

And, surprisingly, the iOS side of things is quite limited too. There is an AirPort app for iOS devices, but this is really just intended to help you install the Time Capsule and set up your new Wi-Fi network. However, you can't quickly back up photos, videos or other files from an iPhone or iPad - not even with the new Files app that was introduced with iOS 11.

Apple's plan - and, of course, Auntie Apple always knows best - is that you use iCloud for backing up and sharing files from your iOS devices. But while iCloud works pretty well these days, there might also be times when you want to quickly upload some new holiday snaps, videos or other files into a shared folder on your NAS drive so that everyone can take a look.

Fortunately, it is possible to use third-party apps that will allow an iPhone or iPad to use the Time Capsule for backup storage, such as the popular FileBrowser, which costs £5.99/$5.99 for the standard edition or £10.99/$10.99 for FileBrowser Business Edition.