Network storage appliances are very popular for providing shared "personal cloud" storage. Naturally, this storage looks very appealing as a backup destination. The thought of backing up all of your stuff without having to plug in a cable is very alluring. "Convenient" and "fast" often go hand-in-hand, but that often is not the case when backing up to a network volume. There are several factors that can greatly reduce the performance of your backup, and this backup strategy encounters several of them.
Backing up your data to a network volume
Before you proceed, your NAS volume should be mounted and accessible in the Finder. Instructions for gaining access to network volumes is available in the macOS Help Center. If your network volume does not appear in CCC's Source or Destination menu, consult the documentation that came with the storage device you are trying to access, or choose "macOS Help" from the Finder's Help menu and search for "connecting to servers".
To back up a folder to a NAS volume with CCC:
- Choose Choose a folder from the Source selector.
- Select the folder that you would like to back up as the source
- Choose Choose a folder from the Destination selector
- Navigate to your NAS volume, then click the New folder button to create a new folder on this volume, e.g. named "CCC Backup". Click the OK button.
- To improve the performance of future backup tasks, click Advanced Settings at the bottom of the window, select the Performance & Analysis tab, then check the box next to Use Quick Update when it's possible to collect a list of modified folders from macOS. Click Done.
- Click the Start button to run the task immediately, or schedule the task to run later.
Note: If you select your whole startup disk as the source to a task that backs up to a NAS volume, CCC will automatically exclude all system-related content. Generally when backing up to a NAS, you should drag a specific folder onto CCC's Source selector to reduce the scope of the task.
Caveats to backing up to NAS storage
Not compatible with Migration Assistant, no backup versioning
First and foremost, backups to a NAS will not be compatible with Migration Assistant, and they do not support backup versioning. If you want those benefits in your backup strategy, you should use NAS storage only as a secondary backup. To create a backup that is compatible with Migration Assistant and supports backup versioning, configure a task to back up to locally-attached storage (e.g. a USB hard drive attached to your Mac).
NAS backups are slow
Backups to NAS volumes are inherently slow because NAS filesystem enumeration is inherently slow. Filesystem transactions to NAS volumes have a high amount of overhead, so even a simple task of comparing folders that have no changes can take longer than it seems it should. CCC's Quick Update feature can go a very long way towards mitigating that slower performance on subsequent backups, but the performance of the initial transfer is mostly dependent on the performance of your NAS and network. We recommend connecting your Mac to your network via ethernet for the initial backup.
Not all data can be backed up to a NAS
Many NAS devices impose archaic Windows naming conventions that prevent you from copying some files to the NAS volume. GarageBand is a classic example – there is a folder named "Aux" in the GarageBand bundle that many NAS devices will refuse to accept.
Because NAS backups have several inherent limitations, we recommend using a NAS for a secondary backup. For primary backups, we recommend that you procure a USB or Thunderbolt hard drive and create a backup on that locally-attached disk. Local backups are much simpler, more reliable, offer the added security of "backup history", are compatible with Migration Assistant, and in general they're a lot easier to restore from.
Some files will consume more space on a NAS backup than on the source
APFS source volumes (e.g. your Mac's startup disk) have files that leverage space-savings features that are specific to APFS. These "sparse" files and "cloned" files can be backed up to a NAS volume, but the space-savings attributes of these files cannot be preserved on a non-APFS volume. As a result, these files will consume more space on the NAS, and will subsequently consume more space if restored back to the original source.