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I'm wanting to have one Mac at work and one Mac at home, each with their own time machine connected to it. No data is to be stored on the Macs themselves, rather, all data is stored on a regular external hard drive that I can move between locations.

When moving the external hard drive and connecting it to one of the Macs, I want the respective time machine to backup the contents of the extenal hard drive onto itself.

Is this setup possible and would it just be a case of plugging things in as described?

Thanks, Andy.

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Time Machine is a software feature and not a hardware device. Time Capsule is a hardware device that is both a NAS hard drive as well as a Wi-Fi home gateway. When you say these Macs have "one Time Machine each", do you mean they each have a Time Capsule, or they each have an external USB/FW hard drive used as a Time Machine drive, or what? – Spiff May 11 '11 at 15:22
'Time Machine' as in an external hard drive, not a capsule. – Andy Cheeseman May 11 '11 at 17:42

You could try installing the operating system on the external hard drive itself and just having it back up to itself before you leave. And when booting be sure just to hold option and boot up into the external.

Just a thought.

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I would recommend installing OS X on an external drive (using the fastest interface possible, like either Firewire 800, Gigabit Ethernet, or Thunderbolt) and moving that around as every Mac can boot from an external drive if you hold the option key during boot-up.

However, to satisfy your backup needs, I believe Time Machine only backs up to external drives so I don't actually know if OS X will see the Mac's internal drive and designate it as an "external". If it did, then this should work fine. If it doesn't, then you can simply use Carbon Copy Cloner to make a incremental backup to another external drive on a regular basis. This is actually preferred in my opinion because you will then be able to boot from that backup too. This would make your downtime almost non-existent if something were to fail with your primary external drive.

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Given the equipment I've got to play with, I think booting to a drive would be quite slow as I've only USB to play with. :( – Andy Cheeseman May 11 '11 at 17:47
All recent Macs have at least Firewire 800 and an Ethernet port. You may have to buy a new hard drive enclosure with those interfaces but it would be worth it if you must do it this way. Otherwise, yes, USB or Firewire 400 would simply be too slow for anything beyond basic computer uses. Usable, but slow. – raffi May 12 '11 at 16:12

Yes, It will work. But the main risk of your strategy lays on your Hard Drive handling. If you let it drop on the floor, or hit-loose-steal it during transport accidentally, you will loose your data and the backup. And it's more likely to happen. If I was you, I will make a second partition on each internal disk of the 2 mac's, and link this second partition to TimeMachine as backup storage space. This way, you will have 2 secured backups of your moving datas.

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If TM1 stays plugged into MAC1, and TM2 stays plugged into MAC2, how would I loose the latest backup if HD1 (Portable HD) is the only drive I'm moving around? – Andy Cheeseman May 11 '11 at 17:45
Ok, it's seems that your are not using the right words : there is time machine*(settings) and *time capsule (or any partition drive). When you said : "I've a time machine on each mac" I don't understand "I have an external hard drive setup for time machine". I though you had configured the time machine pref panel on each mac to have your "data disk" backuped. – Pierre May 12 '11 at 7:58
OK. Sorry. If TC1 is plugged into MAC1, and if TC2 is plugged into MAC2. Would I be able to move an external HD between the MACs and get a backup (via the time machine software). I think my question lies in whether the Time Machine software on MAC1 would screw up the backup for MAC2 if backing up from the same external hard drive. Or are all the settings for TM stored on the respective TC? – Andy Cheeseman May 13 '11 at 10:44
This will work. There no info stored on the backuped volume, so each mac will believe he is the only one to backup your Data Disk. There will be no interference. – Pierre May 13 '11 at 12:58
Great. Thanks Pierre. – Andy Cheeseman May 28 '11 at 22:19

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