Time Machine is a simple and generally effective way to create an ongoing archive of Mac files and folder structure. But it's just a single copy of your data. The same applies to third-party apps that can clone a drive (create an exact duplicate) or create incremental archives that allow you to retrieve a snapshot of the current status of a volume or older versions of modified files. These packages include Arq, Carbon Copy Cloner, ChronoSync and SuperDuper !, as well as many others.
This simple on-site copy is a problem. That is why for many years I have recommended that people also use a cloud-based backup service that has robust encryption. My current top choice for home use for pricing, performance and encryption options is Backblaze, but Carbonite and iDrive are also competitors depending on the features you need. Manufacturers of CrashPlan, Code42 Software, close their personal backup offer, but have an option for small to medium-sized businesses that some people switched to.
Now you might think that on top of that belt and the grids (Time Machine or a local copy plus cloud archives), you should back up the Time Machine volume to an online cloud service. This will give you the best of both worlds, right? An Apple-native Time Machine volume that you can recover through macOS's deep support, and an extra copy of your data. And you want three extra copies (albeit only in two places) of the same data.
Unfortunately, it does not play out in practice. Backblaze specifically omits any volume labeled as a Time Machine backup, while Carbonite discourages it and Code42 explains the downside. iDrive is pretty neutral in the matter. Some of this is a business model: Backblaze includes unlimited storage, as CrashPlan does, while Carbonite and iDrive have maximum storage volumes and opportunities to buy more.
The Problem with Time Machine and Onlne Backup
The most important issue is that Time Machine uses a special type of alias, called a hard link, to create complete snapshots for each time a backup operation occurs. It fails to make a new copy of all files that remain the same between the backcups. These hard links can be displayed multiple times in one volume, but all refer to a single file.
It's smart, but it only works within a single volume. If you back up files from that volume using file-based archiving software, hard links are copied each time they appear. (This also makes it difficult to copy a Time Machine backup from one volume to another without inflating its size.)
Code42 tested how fast Time Machine archives grew at a 53 GB volume on a Mac. Within a week, Mac's Time Machine backup reached 63 GB. However, CrashPlan's archive grew to 303.5 GB. If you have caps or throttles on your broadband data, Time Machine backups can easily push you over, for this reason.
You can run a compound issue: If your Time Machine volume contains other data besides Time Machine Container, some of the cloud archiving services will not back up the non-time machine data! (This column was requested by a reader who encountered the Backblaze problem.)
Here are some strategies for improving and resolving these situations:
Segregate your Time Machine backup. Use Disk Utility to add a new partition (HFS +) or volume in a container (APFS) to the drive containing the Time Machine backup. APFS is easier than HFS + in this regard, because a new volume in a container shares all available space, giving you flexibility. Once shared, you can move your non-Time Machine data to the new volume or partition, and then have the cloud service back up that data.
Rotate Time Machine backup from the site. I recommend using disk encryption for backup drives (Control-click on the drive and select the Encryption element), because at rest a macOS encrypted volume is extremely secure. It can prevent you from worrying about the drive being stolen or investigated when you are not. macOS can automatically back up to multiple Time Machine destinations if they are connected at the same time, but it will also retrieve destinations you reconnect after they are removed. Put one in the safe ̵
Add a clone to your mix.
In my experience, Time Machine works best as an archive – retrieving older or deleted versions of individual files or the contents of folders – rather than restoring a drive. It's also great to migrate from one Mac to another. With external external drives, add one that uses one of the packages mentioned earlier that can clone the contents of the boot drive. These offer all "smart" updates, so that only files that need to be replaced or deleted on the clone are changed every time it runs. I have a nightly clone on my desktop computer and a weekly for my laptop.
This Mac 911 article answers a question sent by Macworld reader Jaxn.
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