On macOS, you can choose to optimize your use of local storage by having your Mac automatically unload files that are already syncing with iCloud Drive, iCloud Photos, and other services. The logic is that you may have limited local storage space and tens to hundreds of gigabytes of data that you don’t always need access to, such as archived documents and photos from past years. You want to have them on demand – with an active internet connection – but not necessarily filling your drive.
However, there is a big caveat: so-called optimized files are only backed up to iCloud. Because there is only a local placeholder for the synced file, Time Machine, third-party sync and backup software, and Internet-hosted backup services cannot make copies.
You might decide it’s good! You trust the integrity of Apple’s data centers and the quality of their operations. While Apple doesn’t provide any insight into how they protect your data, it is certainly true that the copy will have multiple copies of your data stored in three or more different locations to avoid the risk of data loss due to hardware, fire, or other accident, natural disaster. , or a cyber attack or a real attack.
Even if that’s enough for you, read on to make sure your backup strategy is effective.
The Downsides of Relying on iCloud Offloaded Files Only
Making iCloud your only copy for synced data pushed for optimization of your drives or devices has drawbacks:
Losing access to iCloud: You can be locked out, have equipment stolen, your account hijacked or blocked by Apple, and despite the lack of legitimacy you can never gain access again. (You can mitigate some of this risk by enabling iCloud Recovery Data Service.)
Delete items and don’t realize it until it’s too late: iCloud does not keep deleted items for long. Both iCloud Drive and iCloud Photos have Recently Deleted collections (a folder and an album, respectively), but the contents are automatically emptied after 30 days.
Time to recover: Unless you have a fast, unlimited Internet connection at no extra cost, if you need to recover your files by re-syncing iCloud with a new Mac or drive, it can take days or weeks with hundreds of gigabytes of data. It can take hours with a local Time Machine volume.
Unexplained errors: A Macworld reader recently reported that their daughter had lost some music files, despite having Sync Library enabled in Music and an iTunes Match subscription. Even with Apple’s help, they were only able to recover a fraction of the lost files, despite having experienced this before: in a previous failure, all files were recovered. It’s unclear what happened, but these synced files remain missing so far.
You can “game” optimization in one specific way, although you can’t guarantee it will work to back up all the files you want: the most recent files you create or modify will almost always be quickly backed up by Time Machine or an online service that regularly checks for changed files. That will give you an archived copy before macOS may decide to delete the file for optimization.
The best way to make sure you have a full backup using this method is to: do not enable optimization until you run your first full backup on all the services you plan to use.
This strategy won’t work if you need to reset a Time Machine backup or other archive, or if you’re switching between Time Machine volumes to keep an onsite and offsite set. In those cases, you need to disable optimization to create a new full boot backup, which can take a lot of time and bandwidth.
Manage optimization checks
If you want to enable or disable optimization, here are the controls in macOS:
In System Preferences > Apple ID > iCloud (Catalina or later) or in the iCloud preference pane (Mojave or earlier), Optimize Mac Storage controls iCloud Drive storage manager.
In the Photos app in Photos > Preferences > iCloud, you can enable iCloud Photos, but choose between “Download Originals to This Mac” and “Optimize Mac Storage”. I have a desktop and laptop Mac and added a lower speed 1TB external SSD to my Photos library, specifically to keep a local full-resolution copy at all times; see this column. (You can choose a similar option in iOS/iPadOS in Settings > account name > iCloud > photosbut the backup process is very different.)
In the Music app, go to Music > Preferences > General to choose Sync Library. If you have an active Apple Music or iTunes Match subscription, any unique songs stored on your Mac are also synced (and possibly linked) with iCloud. (This 2015 column on syncing music with iCloud remains helpful.)
How Apple Can Help
Apple could mitigate some of the drawbacks I mentioned without compromising our data or our privacy:
Integrate iCloud and local Time Machine backups so that a synced file, image, video, or song was validated as a backup on a Time Machine volume and marked to prevent deletion of that volume before deleting it from local storage .
Create a backup framework for developers to offer the same feature in their software.
Allow internet backup services to connect directly to our iCloud storage with proper authorization and authentication to backup files exclusively stored in iCloud after being “optimized”.
This Mac 911 article answers a question from Macworld reader Joe.
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