I need to replace the original internal SSD (256GB) with a 512GB that has Time Machine on it and up to date.

I am hoping it were not required to involve yet a third disk - e.g. another USB hard drive in this process .. but am not clear on it. Let us call this 1TBdrive

Specifically it seems one solution would be:

  • attach the 1TB hard drive and make it the time machine backup.
  • power off the MBPro and physically swap the 256GB with the 512GB
  • attach the 1TB USB hard drive and boot up, keeping the option button pressed to induce booting to time machine
  • restore from 1TB TM to the new 512GB internal drive

Unfortunately I do not possess this 1TB external drive. So is there any way to do this with just the first two SSD's?

UPDATE Here is the relevant available disk space info

df -k

Filesystem                        1024-blocks      Used Available Capacity  iused    ifree %iused  Mounted on
/dev/disk1                          243915264 235014420   8644844    97% 58817603  2161211   96%   /
/dev/disk7s2                        499771696 214002444 285769252    43% 53500609 71442313   43%   /Volumes/os2mellyrn

Notice the externally attached SSD used for TM (disk7s2) still has 280GB available = more than twice the internal (active) SSD (disk1)

  • Where does the 512 GB SSD reside? In an external enclosure?
    – klanomath
    Feb 1, 2015 at 16:30
  • @klanomath yes a usb attached external enclosure. But i plan to physically swap it with the original internal 256GB SSD Feb 1, 2015 at 16:55
  • How much free space do you have on the external TM disk?
    – klanomath
    Feb 1, 2015 at 17:00
  • @klanomath 280GB. I am updating OP with the "df -k" details Feb 1, 2015 at 17:01
  • So there is enough space on the 512GB drive to include the back ups and a bootable install--which should be possible. If I'm understanding you correctly you want to get the "Working Machine" + "Time Machine Backups" onto the 512GB drive, boot from it and then... do what with the back ups?
    – D.G.
    Feb 1, 2015 at 17:02

2 Answers 2


Sure it works but you have to create, clone/TM-restore and erase various volumes:

I assume your internal disk is disk0 containing disks0s2 as your internal start volume and your external disk is disk1 with disk1s2 as your Time Machine volume.

Without loosing your TM Backup:

This only works if the sum of used space on your TM-volume and used space on your main volume is smaller than ~ 500 GB (to leave some recommended free space on the interim main volume disk1s3). In your scenario the sum is ~449 GB so it works.

  • Add a partition (disk1s3) on the 512 GB SSD with the size ~256 GB (by splitting disk1s2). That should work without erasing disk1s2
  • Clone disk0s2 (your current main volume) to disk1s3 (or restore your TM-backup on disk1s2 to disk1s3), then restart from disk1s3
  • Erase disk0s2 and clone disk1s2 to disk0s2 (or backup disk1s3 to your now new TM-volume disk0s2), then erase disk1s2
  • Clone disk1s3 to disk1s2 and restart from disk1s2
  • Delete disk1s3 and expand disk1s2 to the full size. If that doesn't work start from disk0s1 (your internal Recovery HD) or to Internet Recovery mode and try again.
  • Just reinstall your current system on disk1s2 to create a Recovery HD if none is existing without loosing any (personal) data (e.g if you are running 10.0.2 now just download the latest Yosemite installer and reinstall).
  • Swap the drives

Loosing your TM Backup (not recommended):

  • Erase disk1s2
  • Clone disk0s2 to disk1s2 and restart from disk1s2
  • Just reinstall your current system on disk1s2 to create a Recovery HD if none is existing without loosing any (personal) data.
  • Swap the drives

As I understand the question, you don't need another disk. But be careful if this is your only backup.

It's possible to clone the current bootable drive (256GB) onto the same drive as your Time Machine Backups (512GB with 280GB available), so that it contains a working system and is bootable.

It should possible without third party tools, but it's definitely possible with them.

Take SuperDuper! for example. From their FAQ:

How do I store a bootable backup side-by-side with my Time Machine data?

It's actually really simple. Assuming the Time Machine volume is properly partitioned and formatted for the Mac (as "GUID" for Intel Macs, or "Apple Partition Map" for Power PC), and is boot compatible to start with, just use "Backup - all files" with Smart Update to store a bootable backup on the drive. Your Time Machine backups will be preserved.

CarbonCopyCloner is another example of software which can probably do this, but I've not seen the exact details in their knowledgeable. It could certainly do the cloning, but you'd want to make sure it didn't mess with the backups assuming you have need for them later (moving them off when you get a new larger drive, etc).

But, if you don't need those backups in the future and are prepared to erase them, then you could just format that drive and make a bootable clone of your current system on that drive.

Note: The recovery partition would be a factor here. I'm not sure what, if anything SuperDuper! would do to create one. I know CCC will work with them.

Note 2: If needed you can reconnect your Time Machine with one of the methods explained here.

  • Repartitioning as per klanomath's answer should mean you can use Disk Utilities to do the cloning portion without losing the backups, which avoids any software costs.
    – D.G.
    Feb 1, 2015 at 17:32
  • This is helpful info and I upvoted accordingly. I did award to @klanomath who also had a useful answer : it was a tossup. Feb 1, 2015 at 17:33
  • @javadba No problem. They're subtly different methods too, so it depends which route you want to go.
    – D.G.
    Feb 1, 2015 at 17:35
  • CCC has become much more powerful than SuperDuper and handles the Recovery Partition very well.
    – n1000
    Feb 1, 2015 at 20:30
  • I'm not convinced about the wording on your edit (Note 2) @n1000. The Time Machine is left on the same drive as the OS at that point so you probably wouldn't want to keep using it (and potentially it is still connected because it hasn't moved drives?). The OP established that they intended to start using the other disk for backups after swaping but without using TM, so this (useful!) information is only relevant if the TM is later moved to a new disk and they want to resume using it then?
    – D.G.
    Feb 2, 2015 at 18:41

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