I'm replacing my spinning disk drive with a smaller SSD, because it should make my system much faster[1]. The data I have on the larger drive will fit on the smaller one.

So far, I've done the following:

  • Reboot OSX, holding Command + R, to boot into recovery mode
  • Use Disk Utility to erase and rename the new drive (plugged into USB with a USB-to-SATA adapter cable)
  • Try to restore the main hard drive to the SSD

I get an error like "not enough space on /dev/disk13s2", meaning, I think, "the destination drive is too small." ([asr -source /Volumes/Macintosh\ HD -target /Volumes/the_new_drive -erase -noprompt](http://www.maclife.com/article/columns/terminal_101_make_drive_clone) gives the exact same error.)

Suggestions I've read to fix this are:

  • Use some third-party, commercial software instead. I don't like this option because 1) I think it shouldn't be necessary and 2) I want to limit how many pieces of software and companies I trust with my data
  • Resize the partition on the source drive to be smaller than the destination drive. This scares me. I don't want to lose data. Is it safe?

To be clear: what I want is an exact clone, byte-for-byte. I don't want any changes to file modification times or permissions, etc. I don't want to reinstall stuff. I just want to boot to the new drive and have it work.

Also, I'm using FileVault on the old drive.

I'd love a solution that uses solely built-in Apple tools (like Disk Utility or asr) or something open source.

How can I clone my data from the larger drive onto the new, smaller drive?

[1] I've used iopending to see that pending disk operations are, in fact, slowing me down.

  • 1
    It's the kind of task I've always used Carbon Copy Cloner for, so I'm not posting this as an answer as it doesn't actually answer your question, but it works & it's reliable for anything except Boot Camp, for which the only option is WinClone – Tetsujin Apr 4 '15 at 11:51
  • as CarbonCopyCloner is "just" a GUI to rsync you could take a look at rsync. CarbonCopyCloner though does a lot more than just rsync so In my eyes it's the easiest solution for your problem. on cloning it also takes care of your rescue disc etc. – heiglandreas Apr 5 '15 at 7:52

check my HDD to smaller SSD migration guide at https://apple.stackexchange.com/questions/48798/cloning-a-half-full-500-gb-drive-to-a-256-gb-ssd-drive/117403

There are simple steps and everything is done using standard Mac tools.


Repartition the Source Drive and You Won't Lose Data.

I had the same issue. In my case I had a 498 GB 5200 RPM drive that I was replacing with a 480GB SSD.

There's only about 300 GB of data on the 498 GB drive so I thought I could just create an image file of the source drive and then restore it to the new SSD, but it complained about the SSD drive being too small to restore the backup to.

So, I looked around for a way to "squeeze" the larger disk image into the slightly smaller SSD, but I couldn't find anything. Here's what worked.

  1. Load up the source drive in Disk Image, either in recovery mode (if it's in your device) or as an external USD or something.

  2. Click the Partition button on the source drive.

  3. Assuming you have just one partition, you should see a pie chart showing the single partition and the shaded part indicating the actual used space of the partition.

  4. Create a new partition on the drive that is large enough to make the original partition with the data small enough to fit on the destination SSD. In my case I made a 20GB partition, which made the original partition 478GB, which was smaller than the 480GB SSD drive capacity.

    Doing this will not remove any data. It will only resize the original partition and create a new partition for you.

  5. Once that is complete you can create a new disk image of the smaller partition and happily restore it to the new drive.

As always, make sure you have a backup of everything before you do anything like this to your hardware.

Good luck!

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