Backup External Hard Drive To Another External Hard Drive (On A Mac)

You’re a normal Mac user. Not particularly technical. But you know you should have more than one copy of your files.

You’re already ahead of the game because you take regular Time Machine backups.

Just in case.

But you’ve other files. Special photos, work files on another external hard drive.

Because you need to save space on your Mac’s internal drive.

But that’s the only copy of them. And what if something happened to that drive?

Game Over.

What you need is a copy of that external hard drive.

You need to backup and copy your external hard drive. To another external hard drive ON YOUR MAC.

Can You Backup An External Hard Drive To Another Hard Drive On A Mac?

Or copy one external hard drive. To another separate hard drive on your Mac?

The answer is for sure yes.

You’ll discover in pictures and in a video how.

Read on.

What To Use? For Your External Hard Drive Backup

You’ll find here. How to steps using software you get for free on your Mac.

There are other options.

Paid for software solutions.

You’ll find info on those toward the bottom of this post.

The paid software options are slicker. After all that’s what you’re paying for.

But the downside is you’ll need a version of the software compatible with your Mac’s OS. And we all know that they’ll be an OS update galloping over the hill for your Mac shortly.

And then you’ll have to wait for a compatible version of your software tool to come out.

But you can use Time Machine on your Mac.

Once you know how to use it. It’s easy.

And free.  Because it’s right there on your Mac.

YouTube Video For You: Backing Up An External Hard Drive To Another External Hard Drive On A Mac

Do you prefer to see a video?

Then for you have a video to go along side the how to info in this post. Take a look and see how it’s done on a Mac in 4 minutes 2 seconds.

How To Backup An External Hard Drive To Another External Hard Drive (On Your Mac)

Video Credit: MacTakeAwayData

Choice 1 – Backup Your External Hard Drive And Your Mac’s Internal Drive

Back them up both at the same time.

Useful For When:

You’ve your photos, videos or perhaps specific project files on an external hard drive. Because you needed to free up space on your Mac’s internal drive.

And you have a second external drive.

One you can use as a Time Machine backup of your Mac’s internal drive. And your external hard drive with your other files on.

What You’ll Need:

1. Your Time Machine backup drive must be big enough.

Big enough for all you have stored on your Mac’s internal drive.

Plus be big enough to hold everything you have your external drive. The one with your key files on.

And give growing room to your backup.

Let me net that out for you.

If you’ve 250GB used on your Mac’s internal drive. And 1TB of photos and other files on your external drive. Then you have 1.25TB to backup.

If that’s you. Then, you’re going to need as an absolute minimum a 2TB external drive to act as your Time Machine backup. Preferably 3TB for you to grow into.

Time Machine hates backup space that’s too small.

Not sure how to go about choosing an external hard drive. Take a Look Here.

2. Your new external Time Machine backup drive must be formatted ahead of time.

And the format you need your drive in is Mac OS Extended (Journaled).

If you’re unsure of how to do this then read my document here.

3. You’ll need to plug both your external drives into your Mac at the same time.

Your Mac needs to see both drives.

How To Backup An External Hard Drive On A Mac

1. Have Your Mac Powered On And Your Two Drives Plugged Into Your Mac.

You’ll see those drives on your Mac’s desktop as icons.

2. Then You Start Time Machine Preferences.

To do this you click on spotlight search.

Type in System Preferences.

When your System Preferences come up. Toward the bottom you’ll see a Time Machine image. Click on it to start the Time Machine part of System Preferences.

3. Your Time Machine Setup Window.

When the system preferences part of Time Machine starts. You’ll see the Time Machine setup window.

There are a couple of things to do on the window.

Check these things before you backup your internal Mac’s drive. And your external hard drive to another external hard drive.

Check that the tick box at the bottom is picked to Show Time Machine in the top menu bar. This will be useful later.

You’ll find a check box. On earlier Mac OS releases there’s a slider switch under the Time Machine logo.

Uncheck the box, And if you’ve a slider. Click to turn the slider to OFF.

This will stop Time Machine kicking off a backup while you’re in the middle of setting things up.

The arrows in the picture show you where.

4. Click On Select Disk.

On the next Time Machine window you pick the external hard drive you want to hold our Time Machine backup.

This would be your big drive. The external drive that’s big enough to take your backup of your external drive. Plus your Mac’s internal drive. And big enough for your future backups.

In picture the above it’s the SanDisk 1TB drive.

You’ll see on this window a list of Backup Disks. And Available Disks.

Click on the name of the drive you’re going to use in the Available Disk list.

You can have several backup drives set up for the different backups you want to do. Just give them names that let you easily pick the one you want to use.

Then click on the ‘Use Disk’ button on the bottom right of the window.

You’ve now set up Time Machine to use this drive as the backup drive. The one you’re going to backup your external hard drive and your Mac’s internal drive to.

When you clicked ‘Use Disk’ you’re taken back a window.

If you already had a set up for Time Machine. Time Machine will ask you a question.

Pick to replace your current backup drive with the one you’ve just chosen. You can change it back when your backup is done.

Click the button to replace the current backup drive.

5. Next You Tell Time Machine What You’d Like Backed Up.

Click on ‘Options’.

The standard Time Machine set up excludes all external drives from the backup.

And to backup your external drive you tell Time Machine to include it.

On your Time Machine Options window you’ll see a list.

The way this list works is everything that is on this list is excluded from your backup.

Your Time Machine backup drive. The one you chose in step 4, is on the list.

It’s excluded because it’s the one you’re BACKING UP TO.

But your other external hard drive. The one you want to backup is on the list too.

You want to tell Time Machine to back it up.

In the photo above you’ll see the drive in this example is called SamsungT7.

You’ll see the name you’ve called your external hard drive on the list.

Click on the drive’s name.

Then click minus to remove it from your excluded list.

And then click on Save.

It might take you a few moments to get your head round this.

And Apple has done this in a bit of a confusing way.

Time Machine includes everything on your Mac’s internal drive in your backup. Without you doing anything.

The external drive you want backed up was on the excluded list. Taking it off the list. Means you’ve now INCLUDED it in your Time Machine backup.

And that’s it. You’ve done your set up.

And in a few moments, you’ll set off a backup of your Mac’s internal drive. And the backup of your external hard drive to another external hard drive connected to your Mac.

6. Time Machine Auto Backup. Or Backup Now.

Put a check in the box to start up Time Machine automatically.

Or if your version of the OS has a Time Machine slider. Click to turn from Off to On.

But you can kick off a backup now by.

Heading to your menu at the top of your Desktop screen.

Remember earlier you to checked the box to show Time Machine in the menu bar?

Click on the Time Machine Symbol in your top menu bar.

The red arrow in the picture above shows you where.

Then choose Backup Up Now.

And Time Machine will kick off a backup for you. 

Time Machine may say preparing backup for a little while.

As the first backup of your internal and external drive it could take a while preparing. Don’t worry let it do its thing.

The backup itself may take quite a while.

How long depends on the type of drives you have. And how fast they are.

Be patient and leave Time Machine to back up. Plugging in your Mac to a power outlet means you won’t run out of charge and ruin your backup.

You can check progress at any time. Click on the Time Machine symbol in your top menu and you’ll see where your backup is up to.

7. When Your External Drive Backup Is Complete.

And when you want to plug out the drives.

You right click on the drive icons themselves on the desktop and pick Eject.

Your Mac writes all it needs to down to the hard drives and then you can take out your USB cables.

Choice 2 – Backup Of Your External Hard Drive ONLY To Another External Drive

Let’s say you’re happy with everything so far. But you don’t WANT to backup your Mac’s internal drive to the external drive.

You just want a Time Machine backup of your external hard drive. To another external hard drive on your Mac.

Because you have a backup of your Mac’s internal drive. On an external drive you use just for that.

No issue.

You follow largely the same steps to set up.

But this time you exclude your Mac’s internal drive from the backup.

How To Backup A Hard Drive To Another Hard Drive On A Mac

As before your backup drive must be formatted to Mac OS Extended (Journaled) file system.

If you don’t understand how to do this then read my article telling you how here.

You plug in both external hard drives into your Mac.

Follow Steps 1 to 4 above.

At Step 5 you click on the ‘Options’ button.

You still click on the external hard drive you want backed up.

And click on minus to take it off the list. Same as before.

But DON’T click on ‘Save’ yet.

You want to exclude your Mac’s internal drive from the backup.

And to do that you add it to the excluded list. That way it won’t be backed up.

You do that by:

Click On The Plus Sign.

Add Your Internal Drive.

Then Click On The Exclude Button.

When you’re done click ‘Save’.

And your Time Machine backup settings are saved.

Then you can use the Time Machine symbol at the top of your desktop to kick off a backup now.

When You’re Done Backing Up An External Drive To An External Drive

You can change your Time Machine settings back when your backup is done. Now you know how the principal works and how to do it. 

Why Would You Backup One External Drive to Another Drive On A Mac?

1. When you’ve transferred files, photos or videos. From your Mac’s internal drive. To an external drive to free up space. Without a copy of your files on that drive you’ve a single point of failure.

Hard drives, internal and external SSDs fail at some point. And without a copy you’ll lose your files.

Get yourself the best external hard drive you can find so you can take a backup.

2. When your existing backup drive is producing errors. And you’re worried it might fail. Then you’ll want to save your backups to another drive. Just in case.

3. Because you know if you lose your MacBook. Say someone steals, Or you have a fire, or flood, or you spill your veggie vitamin juice all over your Mac.

Then you’ll want to have a backup you can access.

And a quirk in the universal code of justice says. That when you need your backup drive it fails. Or gives you troubles. So a second backup is an excellent insurance policy.

4. The generally agreed best practice is to have at least two backups of everything. And to keep your second backup elsewhere.

A backup of your external backup drive is one way to do it.

And you can take it to work and store it. Or store at a friends or relatives house. Or in a fire safe.

Because what if you make a silly mistake. And ruin your backup.

Then a copy of your backup on an external hard drive would save your hide.

The Advantage Of Using Time Machine To Do Your External Drive Backup

1. If you’ve a corrupted file. You can use Time Machine to search back through time and find a non corrupted version.

2. Time Machine doesn’t overwrite files when it backs up. If you change a file. Time Machine simply stores the new version of your file. And that means you can go back to the old version.

3. Time Machine takes a full backup the first time it backs up. Be prepared this backup can take a while. But after that first backup the advantage is Time Machine takes incremental backups.

And that means only your changes are backed up. And that makes your next backup faster.

4. It’s inbuilt into your Mac’s operating system so is there. Free for you to use.

Other Third Party Software To Backup Your Drive To Another Drive

There are paid software solutions. Ones that will backup and copy one external hard drive onto another one.

Advantages

• They are specific to this task so you’ve more options available.
• They will allow many backup scenarios/scripts to be created. Whereas your Time Machine set up needs changing between backup set ups.
• The paid solutions allow you network back up options.

Disadvantages

• You have to pay for them, though you do get a free trial period with some restrictions in use in some cases.
• You may find them complex to download and set up particularly if you’re not very technical.
• You’ll need to check and download the compatible version for your operating system. Particularly before upgrading your Mac’s operating system.

The popular ones for Mac are;

• SuperDuper, software
• Carbon Copy Cloner

In Conclusion

In this post you saw how a standard piece of software freely available on your Mac allows you to backup. Not just your internal drive but an external hard drive attached to your Mac.

And an extra backup is perfect if the worst happens. And your external hard drive with your photos, videos or project files on fails.

You can use your Time Machine backup to restore to that drive. Or to a new external drive.

Plus you can use your Time Machine backup of your Mac’s internal drive to boot from. If your Mac’s internal drive fails.

Related Articles

When you need an exact copy of an external hard drive on your Mac. A clone copy of your external drive to another external hard drive may be just what you need. You can read about that here.

The best way of creating a bootable drive is to create a clone copy of your Mac’s internal drive. It’s called a boot drive and this article will tell you how.

And if you want to learn how to restore from a Time Machine backup. You’ll find an article on that too. Just follow this link.

And if you’re not sure how to connect up an external drive to your Mac. Take a look here.