best set up for external hard drive back ups

  Stevenf91 18:58 08 Jun 2018

I have 4 x 4Tb external drives. I want to set up one to store my film collection and one to store my tv shows. The other two i want to set up as back ups so that once a week or once a month i can plug them in and have them automatically update themselves to be a copy of both the other drives. Its a real pain to manually filter through and check what the differences are since the last time I've backed them up. I have came across people talking about a RAID 1 setup but I don't think this is what I'm looking for. It sounds like a RAID 1 needs both drives connected continuously instead of just connecting it the back up drives for a couple hours to back themselves up. Any suggestions?

  bremner 15:29 09 Jun 2018

Time Machine can automatically do what you want. It has been part of MacOS / OS X for many years

  Pine Man 10:14 10 Jun 2018

I use Time Machine which backs up every hour to an external disk and Carbon Copy Cloner which does an incremental back up once a day to an external disk.

  mgmcc 12:08 14 Jun 2018

As I understand it, you are wanting to backup one external drive to another external drive which is different from what Time Machine does; it automatically backs up the drive from which the Mac has booted to an external source. You could use SuperDuper or Carbon Copy Cloner either of which will clone one external drive to another.

I have never found a particularly good File Synchronisation program for the Mac (which doesn't mean there isn't one) but if you have access to a Windows PC, there is a brilliant program called "AllwaySync" which will do exactly what you want.

  bremner 21:10 14 Jun 2018


Time Machine will back up any drive connected to the Mac if you tell it to.

  mgmcc 11:46 15 Jun 2018


Time Machine will back up any drive connected to the Mac if you tell it to.

OK, can you tell me how to configure Time Machine to back up one external drive to another external drive if neither is the boot drive and neither is a backup of the boot drive? I would actually find this useful if it can be done.

  Pine Man 12:45 15 Jun 2018

Having re read the original post it appears that Stevenf91 doesn't actually want to back up his computer at all. Just to create back ups of the back ups he has already created of his Films & TV Shows and, further more, he wants those additional back ups to be differential!

As mgmcc rightly points out this is nothing to do with Time Machine.

I am not sure that I would try to do what is proposed and I have no idea how you would achieve it. I think I would just go for a complete back up of each back up drive and call it a day.

  Stevenf91 22:51 16 Jun 2018

To clarify, I have 4 separate drives. I want to use two of them to store data, (one for films, one for tv shows), which i will leave plugged in to my laptop 24/7. I want to use the other two drives, (drives 3&4), as backs up for the data store on the first two. I would only plug these in once a month or so in order to update them so they are a mirror copy of drives 1 & 2. What I'm asking is, if there is any process or software that will link the drives together and do this for me automatically as at the moment its hard to keep track of what new films or tv shows have been added/deleted and therefore very time consuming (8tb of data) having to manually go through the drive and check for differences between my main drives and the back up.

  Pine Man 08:55 17 Jun 2018

if there is any process or software that will link the drives together and do this for me automatically as at the moment its hard to keep track of what new films or tv shows have been added/deleted

I'm sorry I have no idea how you could achieve that. It sounds as though you would need software to be able to check the contents of one external drive against another external drive to identify differences and then carry out a differential back up. Obviously software exists to make differential back ups from a system drive to an external drive but I don't think you can apply that process to a pair of external drives.

I think you are stuck with making complete copies, unfortunately.

  mgmcc 11:04 17 Jun 2018

You might like to have a look at "Folder Sync" in the Apple App Store which should be able to do what you want.

There is also "Folder Sync 2" which is a free download but then there are In App Purchases which make it more expensive. You do however get a 14 day free trial.

  bremner 08:52 18 Jun 2018


This is how you configure it: -

  1. Connect all drives to the Mac including the Drive You want to Use as Back Up i.e. Drive A

  2. Select Open Time Machine Preferences and choose the Drive A as the Time Machine

  3. In Options exclude all the drives, including the boot drive, that you do not want to backup i.e. click the + sign and navigate to those drives.

  4. Run Time Machine

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