I’m not sure that this is still possible with encrypted disks etc,

Apple charge way too much for SSD space.

I’ve a MacBook and and iMac both specced up with 1Tb SSD’s - this has cost me a pretty penny - and it needen’t have done.

The way I work, I never actually need both machines on. I store all by data in Dropbox and rely on that (or GitHub) to sync between the two devices. So, effectively, I have bought two quite expensive 1Tb SSD’s and I’m running them mirrored.

I won’t be doing that again.

The smart money is on Apple releasing machines with Thunderbolt over USB-C in the late 2016 timescale.

Given that I could buy a new MacBook with large SSD and use that in Target Disk Mode (Press T on power on) to act as a boot disk for my iMac (Press Option / ⌥ / Alt to enable boot menu). The iMac would be configured to boot off this external (MacBook) SSD startup disk and thus I could save the best part of £560 on an internal 1Tb SSD; sweet.

With the external SSD being accessed a Thunderbolt 3 speed I doubt that I would loose much in performance over the internal SSD.

The internal disk on the iMac (Spinning rust platter) could be used for TimeMachine backup and / or a ‘family’ login when I’m away.

PS: Although I could run Target Disk Mode over ‘just’ USB-C, I thing the extra speed offered by Thunderbolt 3 will be worth it.

Pros

• Massive cost saving

Cons

• Can’t use the iMac as an always-on server