Backing up multiple volumes or multiple Macs to a single hard drive can be a messy proposition. If you back up each source volume to the same destination volume without some pre-planning, data from each source volume will be merged in a heap on the backup volume. Additionally, your tasks will archive or delete each other's backed up content. Carbon Copy Cloner can solve this problem! We lay out a few different scenarios and solutions below.
"I want a bootable backup for each computer on the same hard drive"
Creating a bootable backup requires that you provide a dedicated backup volume for each Mac that you want to back up. If you want to maintain each bootable backup on the same hard drive, you simply create a partition for each computer that you want to back up using the Disk Utility application.
Learn more about partitioning a hard drive for use with Carbon Copy Cloner
"I want to back up my startup disk and a data volume to the same backup disk"
If you prefer not to partition your backup volume as described above, you can use two backup takss -- one to back up your startup disk directly to the backup volume for a bootable backup, and another to back up your data volume to a subfolder on the backup volume. Combined with the "Protect root-level items on the target" feature, the two backups will coexist peacefully.
- Configure CCC to back up your startup disk to the backup volume. Choose your startup disk from the Source menu and choose the backup volume from the Destination menu.
- Select "Temporarily archive modified and deleted items" from the preconfigured settings menu.
- Click the "Schedule this task..." button and schedule as desired.
- In the Finder, create a folder at the root level of the destination volume. This is the folder where you will be backing up your data volume, so name it something applicable to that.
- Now configure CCC to back up your data volume to the new folder that you created. Choose your data volume from CCC's Source menu.
- Choose "Choose a folder..." from the Destination menu and select the folder that you created on the destination volume.
- Select "Temporarily archive modified and deleted items" from the preconfigured settings menu.
- Click the "Schedule this task..." button and schedule as desired.
The "Protect root-level items on the target" setting will prevent the first task from erasing the content that you're backing up to a subfolder on that same destination volume.
"My backup volume isn't formatted as HFS+ because I also use it to back up my PC"
There are a couple options for backing up to a volume that isn't formatted as HFS+. If you're only backing up user data — files that reside in your home folder, for example, then you can back up directly to the backup volume. Non-HFS+ volumes often don't support all of the filesystem metadata that is associated with files on an HFS+ formatted volume, but that's generally OK if you aren't backing up system files or files that belong to another user account on your computer.
If you are backing up system files to a non-HFS+ formatted volume, you can back up to a disk image. A disk image is a single file residing on your hard drive that contains the entire contents of another hard drive (except for the free space). When you want to access the contents of that filesystem, you double-click on the disk image to mount the disk image as if it were an external drive attached to the machine. Carbon Copy Cloner leverages disk images to provide you the flexibility of storing several complete backups on a single shared external hard drive. To back up to a disk image:
- Choose your source volume from the Source menu.
- Select "New disk image..." from the Destination menu.
- Unless you're making an archival backup of your data, choose the option to create a read/write "sparse bundle disk image" file
- Specify the location where you want to save the disk image file.
- When you click the Clone button, CCC will create a disk image on the backup volume, back up the specified data, then unmount the disk image when the task is complete.
Note: While disk images themselves are not bootable, you can mount them and restore their content to a physical hard drive to produce a bootable, exact replica of the original.
Learn more about backing up to and restoring from disk images