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I've ordered a 2TB Crucial MX500 SSD to put in my 2012 MBP (A1278) (I'm also replacing the hard drive cable and putting in 16gb of RAM). I plan to install macOS Sierra, followed by Windows 10 (Education edition) with Boot Camp. My question is: Is there a way to create a shared partition on the internal drive for sharing data between the two OS's? I want to have 1250gb for Sierra, 500gb for Windows, and 250gb shared. I know I can use an external drive to transfer files, but I'd like to have a shared partition for data sharing on the internal drive if possible. (The files will be large microscopy image data too large to share on Dropbox.)

My initial thought was to format the whole drive as a GPT drive with a 1500gb HFS+ partition for macOS and a 250gb exFAT partition before using Boot Camp to create a 500gb partition to install Windows (More specifically, formatting the drive with a Windows machine to have two exFAT partitions, and then erasing one of those partitions to HFS+ on a Mac before installing macOS. I got the idea to format the drive using a Windows machine to preserve compatibility after reading this). Does anyone have experience with this? I have read here, here and here that extra partitions on the drive can break Boot Camp. (As an aside, why is this the case? Does Windows get confused about where to boot from?) The authors of the posts I just linked made their exFAT partition after installing macOS and setting up Boot Camp. Would my strategy of making these partitions beforehand work?

Alternatively, user iamthem wrote here that a Boot Camp partition may be shrunk and repartitioned using Partition Wizard in Windows, after setting up the Boot Camp partition. In this scheme, I would format the entire 2TB drive as GPT HFS+, install macOS Sierra, then create a 750gb Boot Camp partition and install Windows 10, finally followed by shrinking the NTFS portion of Boot Camp and creating a 250gb exFAT partition with Partition Wizard (while booted under Windows in Boot Camp). Does anyone see any problems with this scheme?

I have an external hard drive enclosure, so I can do a lot of this before actually putting the drive in my laptop. Thanks for your input.

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Install Sierra (or newer) on your SSD, then boot into it and use Boot Camp and set it to allocate 500G. Boot Camp will handle splitting that volume into 1500G HFS+ and 500G NTFS.

Once that is complete, from your Mac launch Disk Utility and...

  1. Select the Crucial physical media.
  2. Click on Partition.
  3. Ensure the HFS+ pie slice is selected.
  4. Click the Plus sign.
  5. Enter 250G and change the Format to exFAT.

You should be left with 1250G HFS+, 500G NTFS and 250G ExFAT.

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I'm not sure this is a full answer... but here are some things you can't do...

If you add the ExFAT first, Boot Camp Assistant will refuse to repartition.
Apple's Disk Utility will only allow a maximum of 4 partitions on a drive; there are already 3 before you start this, EFI, Recovery & Macintosh HD.

If you touch the partitioning from inside Windows, you will break the whole drive.
Super User & Ask Different are both littered with hundreds of disparate ways people have managed to do this & been unable to fix it without just wiping & starting over. We did have one guy on AD who could actually do this by hand from Terminal, giving specific answers for specific fail-cases [& occasionally working over TeamViewer for particularly tricky ones] but he doesn't seem to be around so much these days. That's one guy I've ever met who can fix these things, out of all the people on here - some of whom are very clever indeed.

For many people, their go-to solution is rEFInd - freeware. There are many tutorials on this, but there are also many failed cases on SE with similar results to above.

Unless you really feel up to the task of in effect 'knitting your own hard drive' then the smart money is on
Paragon - Hard Disk Manager
Paragon - CampTune &
Two Canoes - WinClone

Each of these can handle Boot Camp partitions without breaking anything. There are no other apps I'm aware of that can do the same tasks.

They each do slightly different things, so which you choose is up to you [I actually ended up with all 3, for those 'just in case' occasions] - Paragon I know does a fully-working trial version, I'm not sure about Two Canoes.
Full backups of any existing data should, of course, be in place before starting.
You could experiment to see which would be your best long-term or repeatable solution.

I have no affiliation with any of the above products - merely a happy user.

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