If you’re thinking about making more use of iCloud, either as iCloud Drive or by letting macOS Sierra decide what files to ‘optimise’ to free storage space, two major considerations are backing up those files (Time Machine), and searching their content (Spotlight). This article looks at how using iCloud to store documents affects those. Although Apple explains some of the iCloud options here, it does not make clear their effect on backup and search.

Backup

If your Mac makes Time Machine backups, and you store files on your iCloud Drive, then you should have backups of those files as part of your Time Machine backup.

The snag is that accessing those backups is not as simple as it should be. If you open the Time Machine app (used to restore from backup, not the pane in System Preferences), drop back a backup or two, to one from earlier today, and then click on the iCloud Drive icon in its Finder-like browser, you will (probably) not see the contents of your iCloud Drive at the time of that backup.

To browse the backups made of your iCloud Drive, you need to open that location in the most recent Now backup in the Time Machine app, and with iCloud Drive selected and its contents displayed, you can then browse back through time and see the changing contents of your iCloud Drive. It is hard to know whether this is supposed to be a feature, or is just a plain bug.

Files which macOS Sierra has moved to your iCloud storage to free up space work differently. In order to qualify to be moved, they must not have been altered (possibly even accessed) for longer than other files in your Documents folder and on your Desktop. So they should already be backed up from before that, and exist within your Time Machine backup.

If you decide to edit documents which Sierra has moved out to iCloud storage, that should result in their being returned to local storage, so they should reappear in your Time Machine backups again.

As this feature is new to Sierra, you would be wise to ensure that all old and important documents which Sierra could move out to iCloud are already well backed up, just in case.

Search

Spotlight’s background metadata indexer, mdworker, works its way through all files which are accessible through your Mac’s file system (the /Volumes folder), unless they are in a location which is on the Spotlight exclude list, which you access in the Privacy tab of the Spotlight pane. By default, your iCloud Drive is not excluded from Spotlight search, so the contents of that storage will be indexed into Spotlight’s hidden index files, and will be included in search results.

If you want to exclude iCloud Drive files from indexing and Spotlight search, you can always add the drive to the exclusion list in the Privacy tab. There are reports that there may be a bug which prevents that from working, for some users, and that Spotlight will always index your iCloud Drive, and return search results including its contents.

If Sierra moves documents from local storage to iCloud to free space, it leaves behind special stub files to mark those documents which have been moved. mdworker and Spotlight should recognise those, and include moved documents in both indexing and search (unless they are in an excluded location). I have not seen any reports that this does not work as it should.

Security

Apple details here the measures used by iCloud to maintain the security of the files which you store there. For iCloud Drive and backup, data are encrypted in transit between your Mac and iCloud, and stored in encrypted form on the iCloud servers.

In practice, the greatest threat to the security and privacy of those files which you store in iCloud is the security of your password. If your Apple ID and its password are easy for someone to guess, and you do not have additional security measures (two-step verification) enabled for your iCloud account, then it is much more probable that an intruder will break into your files by guessing or stealing your username and password.

Note though that, if you are legally required to comply with data protection law (in the UK, the Data Protection Act 1998, and coming soon to the whole of the world, the EU’s new GDPR rules), storing protected personal data on iCloud may not satisfy the requirements of the law. Whoever is responsible for overseeing your compliance must give specific approval to any such use, that it meets your organisation’s implementation of the legal requirements.