Multiple Macs backup up to one External HD

If you are going to partition the backup disk, then you have a copy of SuperDuper on each Mac, and take the backup disk to each Mac, plug it in, and run SuperDuper to that Mac's backup partition. This will create bootable clones for each Mac.

If you want to use a Sparse Disk Image, which is NOT bootable, and would be more involved in restoring your data. In the Sparse Disk Image model, you do not need to partition the backup disk, as Sparse Disk Images are just regular files on any storage device. The advantage of a Sparse Disk Image, is it only takes the amount of space needed to backup what you have on the Mac being backed up and you do not need to partition. The disadvantage is that it is more work to completely restore a Mac. Just restoring a few lost files is easy, it is restoring everything, including the operating system that is a pain with a Sparse Disk Image.

To mitigate the problems of restoring a Sparse Disk Image model, you could create 1 partition where you could create a bootable clone of the newest macOS version that will run on "ALL" your Macs, then the rest of the disk space would be for Sparse Disk Images. If you have to restore everything for a Mac, you would boot the bootable clone, and run SuperDuper to restore the Sparse Disk Image to the Macs boot disk.

There can be lots of different backups approaches, and they can get messy. This is why Apple provides Time Machine with a simple 1 external disk per Mac and macOS manages everything. When you move away from that, things get "Interesting" 🙂

As to using the left over disk space for an extra partition where you would put Sparse Disk Images, and the other partitions would be bootable clones. You can do that, but it seems a bit redundant, as a sparse disk image contains the same data, stored in a different way, on the same disk. So having 2 copies of almost the same information doesn't really help you if you loose the backup disk. You could compromise, in that you could do bootable clones for those Macs that you MUST have available and back in service as soon as possible, by booting the bootable clone, and for the Macs that can wait until you get-around-to-it, you could use Sparse Disk Images, and use one of the bootable clones to aid in restoring the Sparse Disk Image. See "Interesting" 🙂

It is a poor strategy. If the disk fails you lose all the backups for every computer. The proper way is one backup drive per computer.

Basic Backup

For some people, Time Machine will be more than adequate. Time Machine is part of OS X. There are three components:

1. A Time Machine preferences panel as part of System Preferences;
2. A Time Machine application located in the Applications folder. It is used to manage backups and to restore backups.
3. Time Machine requires a backup drive that is at least double the capacity of the drive(s) it backs up.

Alternatively, get an external drive at least equal in size to the internal hard drive and make (and maintain) a bootable clone/backup. You can make a bootable clone using the Restore option of Disk Utility. You can also make and maintain clones with good backup software. My personal recommendations are (order is not significant):

1. Carbon Copy Cloner
2. Get Backup
3. Deja Vu
4. SuperDuper!

Visit The XLab FAQs and read the FAQ on backup and restore. Also, read How to Back Up and Restore Your Files. For help with using Time Machine visit Pondini's Time Machine FAQ for help with all things Time Machine.

Although you can buy a complete external drive system, you can also put one together if you are so inclined. It's relatively easy and only requires a Phillips head screwdriver (typically.) You can purchase hard drives separately. This gives you an opportunity to shop for the best prices on a hard drive of your choice. Reliable brands include Seagate, Hitachi, Western Digital, Toshiba, and Fujitsu. You can find reviews and benchmarks on many drives at Storage Review.

Enclosures for FireWire and USB are readily available. You can find only FireWire enclosures, only USB enclosures, and enclosures that feature multiple ports. I would stress getting enclosures that use the Oxford chipsets especially for Firewire drives (911, 921, 922, for example.) You can find enclosures at places such as;

1. Cool Drives
2. OWC
3. WiebeTech
4. Firewire Direct
5. California Drives
6. NewEgg

All you need do is remove a case cover, mount the hard drive in the enclosure and connect the cables, then re-attach the case cover. Usually, the only tool required is a small or medium Phillips screwdriver.

It is a poor strategy. If the disk fails you lose all the backups for every computer. The proper way is one backup drive per computer.

Having a backup is good. It is MUCH better than no backup, which will put you miles ahead of many other users.

And if the backup is really just a backup, and not an archive where you expect to find data you do not have stored anywhere else, then if you loose the backup device, you just replace it, and make a new backup from each Mac. During the period of time when the backup has failed, you are unprotected.

And if you are going to use a networked backup approach, it is far easier to have a large storage device on a backup server (dedicated Mac, or a NAS, such as a Synology.com device).

Now if you want to evolve to more than one backup device, you can alway get a second drive in the future and then rotate backups to the devices. That would mean if you loose one backup device, you still have a copy of all your Macs on the other backup device. Add a 3rd backup device, and you have 3 layers of backup. At that point you would be so far ahead of users that do not backup, you would not even be able to see them in your rear view mirror 🙂

Using a RAID device, such as a direct attached Drobo would give you a little more reliability, as the RAID would survive if one of the RAID disks failed. Also something like a Drobo would allow you to increase the storage by either adding more disks, or by replacing older smaller disks with larger capacity disks.

You would get RAID protection with most NAS devices, such as a Synology.com network server.

Again, whatever you do, having a backup is way better than not. And the easier it is to make the backups on a regular basis, will mean you do it and do not have an out-of-date backup that does not contain recent work.