This hint collects together what I have learned about solutions for Time Machine backups. There are a number of viable solutions, and I cover several of them.
External USB or Firewire drive
The most basic solution is a directly-attached external USB drive enclosure. This might be okay for desktop machines, but what bothers me about this is that both the Mac and the drive are on the same power circuit. If lighting strikes, then both can get hit at the same time. In a Mac Pro, you can use another internal drive for TM. And there are also external RAID solutions like I mention below. Unless you are particularly disciplined, this is a lousy solution for portable Macs. When I was going this route, I was lucky if I remembered to plug in the backup drive once a week. Maybe other people can do better than that, but it's still inconvenient.
Thus, I prefer networked solutions. However, at the end of this hint, I go into a discussion on why TM is a great design for local backups, but a major source of unreliability for networked backups.
If you want to do Time Machine backups over a network, then Apple's primary supported configuration is Time Capsule. I'm not happy about that, because Time Capsules have a history of being unreliable. Back in 2009, there was a wave of failures. A web site
was set up to track the failures. This site is either abandoned, or there haven't been any failures since early 2010. Maybe TC has gotten better, but the fact of the matter is, it's a single-disk system with inadequate ventilation and cooling. People still report them getting very hot. Mechanical drives are already a ticking time bomb -- letting them get hot accelerates that process significantly. The heat also plays havoc with the other electronics, and many failures have left the drive intact but inaccessible. You could get a replacement unit from Apple, but you could not salvage your data, because removing the drive would void your warranty.
Once upon a time, Apple sold a blade server called Xserve. That may have been part of a reasonable TM solution for a corporate environment. But with the demise of any sort of dedicated Apple server platform, there is no longer a good centralizable solution for TM backups for a large number of Macs. In a corporate environment, therefore, you must decide if you want to provide every desktop with its own external backup drive and badger the notebook users to plug it in periodically. Or set up a Mac Pro with some huge drives crammed in it and hope it works reliably as a server. For a home user, if you have a desktop Mac and a notebook, you can connect an external drive to the desktop and backup the notebook wirelessly. You just have to make sure that the desktop is awake whenever you want to backup the notebook, which is only slightly more convenient than just plugging the notebook into its own backup drive.
The most convenient solution is some kind of Network Attached Storage (NAS). Unfortunately, Apple's support for that is limited to their own sanctioned solutions.
Airport Extreme Base Station with external USB drive
Another option is a USB drive attached to an Airport Extreme Base Station (AEBS). This isn't officially supported by Apple, although the firmware supports all the necessary Apple Filing Protocol (AFP) features for Time Machine to work reliably. There, the weak link is the drive itself. There are a lot of external USB drive options, like WD's MyBook, but most of those solutions aren't intended for extended use. If you back up three Macs to one drive, then that drive is going to spin up three times an hour, and spin-ups cause wear and tear to desktop drives. On the other hand, if the drive spins continuously, unless the external enclosure has a fan in it, then it's going to heat up, with the usual consequences.
I would recommend a RAID solution like the LaCie 2big Quadra. (There's a switch on the back to select a RAID 1 configuration.) This actually costs more than a TC of the same capacity, but that's because there are two drives, providing redundancy. If a drive fails, open up the unit and replace it. If the logic board fails, pop the drives in a replacement enclosure. You can connect a drive to the AEBS via USB, and it appears as a Time Machine supporting volume with no hassle. If you're willing to spend the money, I think this may be the best solution overall.
Linux or Windows Server
With Linux, you have a few options for serving files, including NFS, SMB, and AFP. For Windows, you have built-in SMB support, and there are NFS solutions as well.
The most obvious solution for Linux would be to use an AFP server, like Netatalk. AFP is more efficient than SMB and therefore faster over high speed networks. Unfortunately, Netatalk has some serious drawbacks:
- It suffers from random authentication failures. Every Mac I have will randomly fail to authenticate once out of every 5 or 10 connection attempts, and I'm not the only one with this experience. My attempts to debug have failed because doing things like enabling debug messages mask the problem. I've reported this bug, but I was told by the Netatalk devs that they're only interested in looking into it if a corporate customer encounters the problem. The occasional failed authenication, however is really a minor problem. Netatalk can supposedly use Kerberos authentication directly, but I've never been able to get that to work.
- Netatalk doesn't support Replay Cache or TM Lock Stealing, two features essential for reliable TM backup over a network.
- As a result of the missing Replay Cache feature, if you attempt to put a Mac to sleep during a backup, it will LOCK UP HARD. This is obviously a bug in MacOS, but it nevertheless eliminates Netatalk as a viable solution for Time Machine.
I've experimented with trying to use NFS for TM backups, but I couldn't get it to work. For one thing, even if you advertize the share using Zeroconf/Bonjour, MacOS won't see it. It worked with Tiger, but it's been broken ever since, so I think this is intentional.
If you manually mount the NFS share, TM will see it (if you have unsupported volumes enabled) at the time you have it mounted and let you select it for backup, but it is unable automatically mount it later when it's time to do a regularly scheduled backup. (Just 'Making backup disk available...' indefinitely.) If you're on a desktop Mac, you can use automount for NFS, but this isn't a solution for portables. MacOS's support for SMB is buggy and slow, but it's easy to setup and seems to be the only viable alternative to AFP. Therefore, the rest of this hint covers using a SMB server (Linux or Windows) to store Time Machine backups.