MacBook – Performance of MacBook Air SSD Targeted from iMac

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I use a MacBook Air, but would like to put an iMac at my office for a performance boost. I don't want to switch between operating systems, so I'd like to target the Air's SSD (via Thunderbolt 2) when working from the iMac. Here are the devices:

  • 2015 13" MacBook Air i7, 2.2GHZ, 8GB RAM, 512 SSD (Thunderbolt 2)
  • Retina iMac i7, 4GHZ Quad, 32GB RAM, (Thunderbolt 2)

My dream is that I'd be using the iMac's RAM & processor, and that Thunderbolt 2 would be fast enough that I wouldn't lose any SSD performance.

For me latency matters more than throughput, but I'm interested in both. Processing thousands of small files at once, not editing video.

Would this work? (theory, experience, benchmarks welcome)

UPDATE: I'm adding a bounty for anyone that can offer actual benchmarks of targeting a MacBook Air (or pro) SSD from a retina iMac (via thunderbolt 2).

To be totally clear – I'm only interested in "Target Disk Mode" performance. I want to run the Air's OS. I already know about file syncing, external drives, etc. Thanks everyone for the ideas though.

Best Answer

So I tried it out and wanted to share my findings. First off, the equipment I was using:

  • Early 2015 13" i7 MacBook Air, 8GB Ram, 500GB SSD
  • Late 2015 27" i7 iMac 5K Retina, 16GB Ram, 1TB SSD

I restarted the Air in target disk mode & plugged it into the iMac via Thunderbolt 2. It wouldn't boot. After a few minute, it just showed a ban icon (circle with a line through it).

I ran some 5GB Blackmagic Speed Tests to gather transfer rates (in MB/S):

  • iMac against its SSD - 1817 Read, 1510 Write
  • Air against its SSD - 300 Read, 241 Write
  • iMac & Air against USB3 Flash Drive - 245 Read, 185 Write
  • iMac & Air against USB3 External Drive - 160 Read, 170 Write
  • iMac using Air via Thunderbolt 2 shared folder - 400 Read, 490 Write
  • iMac using Air in target disk mode - 79 Read, 107 Write

So obviously there's a big performance loss for target disk mode.

If you're wondering why I'd want to target the air, it's because I mainly work off my Air and don't want the hassle of an external drive, thumb drive, file syncing, etc. I love the idea of getting to my office and "docking into" a faster processor, more RAM, and a big screen.

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