Take the 2-minute tour ×
Ask Different is a question and answer site for power users of Apple hardware and software. It's 100% free, no registration required.

Before I buy a new SSD, I wanted to see if the following is possible:

I have a 500 GB HD in my MacBook Pro that is using only 240 gigs. Can I clone this to a 256 GB SSD drive? (My goal is to replace the boot spinning drive with an SSD drive.) Then use the 500 GB HD as a second drive in the SuperDrive bay.

Can I clone to the SSD if it's in a USB enclosure as well?

And what is the best cloning software?

I'm running OS X Lion, if that's useful.

share|improve this question

4 Answers 4

up vote 4 down vote accepted

You can do that, however having so little space left on the SSD after cloning might be an issue when you start running the machine.

You can use either Disk Utility (in Utilities, or better, you could start from the Snow Leopard DVD and start it from there); SuperDuper! (I've used that), or Carbon Copy Cloner. But be very careful, make sure that you don't switch the source and target (you'll lose everything) and make sure that you can boot from the SSD and that everything works before deleting the old drive. Find some tutorials (SuperDuper and Carbon Copy Cloner have them on their websites) print them and make sure that you understand each step before proceeding with the cloning.

Alternatively, if you can find or borrow another disk, you can create a Time Machine backup of the internal disk, replace it with the SSD and restore from Time Machine. It would be slower, but you'll have an extra copy (the Time Machine disk) just in case.

share|improve this answer
Time Machine would be easiest. So it can restore to a smaller drive? –  BahaiResearch.com Apr 16 '12 at 18:13
I think so, although I've never tried that. It doesn't actually clone a disk (as in create an image or exact copy), but you could restore to a new disk as if it is restored from image. But for Time Machine you'll need a third disk to use as Time Machine disk. –  lupincho Apr 16 '12 at 18:37

You can do a couple of things if you intend to use an SSD in addition to your regular drive.

Firstly, using Disk Utility is likely to be the easiest way to clone it, so long as you are sure that it will fit. Open Disk Utility, select your existing disk, and click the "restore" button in the top right. You will have something like the following screenshot, although in my instance I do not have any other disks.

enter image description here

In your own window, you will see your SSD disk in the left hand column. Drag it's name into the destination field. This will create a copy of the source disk, onto the destination disk. You may need to partition your SSD first - ensure it uses the same GUID partition scheme and options as your existing drive.

Next, prove you can boot from it. Hold the Option key down, and select the SSD to boot from. It should be identical, but way faster.

Now, you can choose how to take advantage of it, and your other disk. As you are already nearly full on your boot drive, you need to clear some stuff off it. A good choice for things that don't necessarily require speed are your iTunes library and iPhoto library, as well as any iMovie files. These are most people large file collections, and there isn't usually much requirement to have them accessed lightening fast.

Moving such data and folders around is one way to clear up a chunk of space to leave your SSD room to "breathe" without worrying about filling it, but it's a manual process that can be prone to error, as well as confusing for backups etc.

Another thing you can try is moving your entire home folder. Luckily, you don't even have to move it to test this option. Go into preferences, and locate your user. Right click on your name on the left column, and click advanced. You will see an option to store your home folder elsewhere. Click choose, and point it at your old disk. It will now boot from your SSD, but use the old drive for your home folder. This effectively moves all your data, but none of your apps off the SSD, which is a simple and efficient way to get a good balance between speed and capacity requirements. If you have large apps that don't need speed, you can move them into your home folders app folders to get them off the SSD too.

enter image description here

Once you have done this, and proved that it all works fine, you have some cleanup to do. You can either just wipe the old disk, then re-copy and delete (move, effectively) your home folder back into it, of you can manually just remove the hold folder on your SSD, and all the OS folders on the original disk expect your home folder.

There are millions of ways to skin this particular cat, this is just one (albeit the simplest one), and its what I intend to do as soon as my optibay arrives :)

share|improve this answer

What is the useable disk space of your 256 GB SSD when it is formatted for Mac, but empty? I'll bet it's quite a bit less than 256 GB.

It is a general rule of thumb that hard drives do not work efficiently unless at least 15% of the volume of the drive (as formatted for your OS) is empty space. This is necessary for file defragmentation, a maintenance operation which Mac OS X performs automatically in the background.

So you should not put more than about 217 GB of data on a hard drive that has 256 GB of capacity when it is formatted but empty. If you actually have a full 256 GB to use, at least 38 GB should be left empty. If you do fill up more space than 217 GB, your computer will work, but the performance of the computer will become slower over time due to data fragmentation.

share|improve this answer

I'd clean off at least 20GB from the hard drive. Then install a clean OS to the SSD and use migration assistant to move the rest of the drive over to SSD.

I found that after a few years, the Mac just slowed down. Installing a fresh OS and then migrating apps and files improved performance quite a bit. Why move clutter along with the files you want?

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.