Choose Local or Network Backups
Before you go too far in designing a backup plan, you should take a moment to ponder whether you’ll back up to a local storage device (that is, one connected directly to a Mac with a cable) or to a device located somewhere else on your (wired or wireless) network—or both.
In years past, I assumed that in most cases each Mac would have one or more backup drives of its own, and that network backups were mainly for locations with more than a few Macs or with exceptional backup needs of some sort. Now, however, network-based backups of one sort or another seem like a good fit for a wider range of people.
In this brief chapter, I help you think through the pros and cons of both local (DAS) and network (NAS and server-based) backups. Whichever approach (or combination of approaches) you choose, your decision will help inform which software and hardware you use; I discuss those choices in the next two chapters.
Local Backups
With a local backup, you plug your hard drive or other storage device into a Mac and let your backup software run. (Time Machine starts automatically, as do some third-party backup apps; other software requires either an explicit schedule or that you manually run backups after attaching a drive.) When it’s done, you can disconnect the storage device and hook it up to another Mac if you have one.
If you want to make bootable duplicate, you’ll need a local storage device (preferably an SSD), because starting in Catalina, it’s no longer possible to make bootable duplicates over a network; see the sidebar So Long, Bootable Duplicates over a NetworkFor versioned backups, meanwhile, the main advantage of a local storage device is speed, at least if you’re using a fast interface (such as Thunderbolt 3). However, as I explain just ahead, nowadays the speed difference versus a fast network is small enough that most people won’t notice it.
The downside to local storage is that backups and restorations can occur for a given computer only while the drive is connected, and if you forget to connect the drive, you won’t have a backup at all. You may end up doing a lot of plugging and unplugging—and more so if you’re moving a single drive between computers. And, if you have a laptop and you actually use it on your lap (as opposed to a desk), having an external drive attached can be a real hassle.
Keep in mind that local storage need not be a single external hard drive or SSD; it could be a RAID or other multi-drive assembly—any type of DAS. See Decide on a Storage Configuration for further details.
Network Backups
In a network backup, one computer (or other device) typically functions as the backup server—the machine to which your backup drive(s) are physically connected. Files from your other computers (which function as clients) are copied over the network onto each backup drive.
If you have multiple computers—especially if one or more of them is a laptop that gets moved around a lot—network backups can be far more convenient than local backups that require being physically tethered to an external drive. They require virtually no intervention; just leave all the necessary devices turned on and, assuming you have your backup software configured appropriately, the computers on your network will back themselves up automatically as needed.
For a long time, conventional wisdom held that network backups would always be slower than local backups—and, moreover, that network backups could cause sufficient congestion to slow down other things on your network to unusable speeds. Although a directly connected Thunderbolt 3 or 4 drive will indeed give you much faster performance than even an 802.11ax (Wi-Fi 6 or 6E) connection or a 10 Gigabit Ethernet wired connection, real-world network performance these days is usually fast enough that the average user won’t perceive backups or network operations as being too slow. In my opinion, network backups are fast enough for most people, most of the time, and speed is essentially a nonissue.
Network Backup Approaches
Network backups can proceed by any of four different methods:
Push: The server—a computer or a NAS device (see Network Storage Devices)—shares its backup volume (see Share a Volume), which the client machines mount as a volume in the Finder. Then each client computer uses its own backup app to back up files to the network volume (rather than to a locally attached drive). This is sometimes called a push backup, since each client “pushes” its data onto the network volume.
Pull: Each client Mac shares the volume(s) to be backed up. The server mounts these volumes in its Finder, and then the backup app, running only on the server, copies files from each network volume onto its locally attached backup volume. This is sometimes called a pull backup, since the server “pulls” data from each of the clients onto its backup volumes.
Client-server: The server runs backup software that supports client-server network backups, and the other machines run client software that communicates with the server directly—usually without any of the machines having to share or mount volumes. Retrospect Desktop is the best-known example of client-server backup software, but Carbon Copy Cloner and ChronoSync (among others) also support client-server backups of sorts.
Any Mac running High Sierra or later can function as a Time Machine server on your network, providing a storage place for backups from all your Macs without the need to mount network volumes as in a push or pull backup. You can even configure where Time Machine backups are stored, how much space they’re permitted to occupy, and more. For instructions, see Use a Mac as a Time Machine Server. Most modern NAS devices can also function as Time Machine servers; see Network Storage Devices.
Peer-to-peer: Each computer on the network runs backup software that can act as both a client (backing up that computer’s files to other computers) and a server (hosting the backed-up files from other computers)—again, with no need to share or mount volumes. When two or more computers use software that allows mutual backups of this sort, it’s called peer-to-peer backup. Given that CrashPlan exited the consumer market long ago and Synk is no longer being developed, I’m not aware of any great options for peer-to-peer Mac backups right now. (ChronoSync comes fairly close, but it falls short of a true peer-to-peer model.)
Any of these approaches can work under the right conditions, but most of us will use either push backups or client-server backups, the latter of which tends to be more reliable and is also the setup most likely to support Windows and Linux computers. Be aware that when a backup depends on a remote volume being mounted in the Finder (as in pull backups and some types of push backups), quite a few things can prevent that from occurring as expected, with the result being failed backups. That’s just one of many reasons to consistently Test Your Versioned Backup.
Network Backup Considerations
As you consider whether to use a network destination for your backups, keep these facts in mind:
It probably goes without saying, but I’ll say it anyway: the storage device you use for network backups must have sufficient free space for all the computers you plan to back up. (See Decide on Capacity.)
Time Machine can see a network volume only if it’s attached to a Mac or a NAS device that’s expressly designed to work with Time Machine. In other words, if you choose Time Machine as your backup software, you need to be pickier than you otherwise would about what type of network storage you use.
To make an external drive (connected directly to your Mac) available to other computers on your network, you must share it. See the sidebar Share a Volume, just ahead, for instructions.
For a scheduled network backup to occur, both server and client machines must be turned on and awake. (Read the sidebar Power Management and Backups for advice on how to wake a sleeping Mac for a backup.)
Local vs. Network Backups: Joe’s Recommendations
I can’t make a one-size-fits-all recommendation when it comes to selecting backup destinations. The number of computers you have to back up, the amount of data they store, your network configuration, your budget, and your tolerance for complexity all factor in. However, I would like to offer the following suggestions:
If you want to have bootable duplicates, you’re going to be using local storage (preferably a Thunderbolt 3 or 4 SSD, if your Mac has Thunderbolt 3 or 4 ports) for those. If you can buy a large enough SSD, you can also use it for versioned backups, but you might find it more cost-effective to use an external hard drive, a NAS, or other network storage for versioned backups.
If you have just one Mac, the path of least resistance is to store your versioned backups on a directly attached storage device. If your single Mac is a laptop and you can’t bear to fiddle with the external drive and cables, a simple, inexpensive NAS device is your next-best option.
If you have multiple Macs and saving money is your priority, a large external drive is your best bet for versioned backups. You’ll have to shuttle it around, plugging and unplugging as necessary—and you’ll have to make sure you choose an interface that’s compatible with all your Macs (see Choose an Interface).
If you have multiple Macs, one of which is always kept in the same place (so an external hard drive can remain connected) and always turned on, that Mac can function as a backup server for the rest.
You can then do any or all of the following with this Mac (in order of my preferred options):
Use it to host Time Machine backups; see Use a Mac as a Time Machine Server.
Run the server component of another client-server backup app, such as Retrospect Desktop, while your other Macs run the client.
Share a backup volume, which other Macs on your network mount and copy data to using backup apps they run (push backups).
Mount volumes shared by other Macs and copy data using a backup app on the server (pull backups).
If you have multiple Macs but none of them is available to function as a backup server, or if you want an all-purpose storage pool for your network, a NAS device—with enough storage for all your Macs and then some—is a great choice for versioned backups; see Network Storage Devices.
Once you’ve decided whether to store your backups locally, on a network volume, or both, you’ll want to select the appropriate software (which I cover in the next chapter, Choose Backup Software) and hardware (see Choose Backup Hardware).