I would like to setup my Macbook Air's disk drive with 3 partitions - 50Gb for OSX Lion, 50Gb for Windows 7, and the remaining 150Gb for Data to share between both OSes (music, photos etc).

What's the correct way to do this?

  • Perhaps you should just settle for two paritions, and use third-party software on Windows and/or Mac to enable one OS to access files in the file system of the other. Then put all your media files on one partition. There are resources on using this sort of software on MacWindows.com. Products for enabling Mac OS X to read and write to Windows NTFS storage Products for enabling Windows to read and write to Mac HFS+ storage – user9290 Aug 21 '11 at 18:43
  • I would love it if you kept the question simple and answered this with the attempts - it shows great knowledge and will be much more useful. If someone sees an error - they are more apt to fix a 95% correct answer. TL;DR questions get killed whereas short Q and long A are the goal here. Don't worry the answer isn't correct (yet) - do keep the Q/A division clear – bmike Aug 25 '11 at 20:28
  • Matt - make sure you let me know via comment (in three days time) if anyone has the best answer - I'm happy to deliver the bounty to the most useful answer for you rather than for me... – bmike Sep 1 '11 at 19:40
  • HuzZz got my vote - it finally worked! After 6 or 7 attempts. I think why my previous attempts didn't work was because I had the Bootcamp partition as the 2nd one and not the 3rd. – Matt Frear Sep 1 '11 at 20:09
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    I'm wondering if with OSX Mavericks, Windows 8, UEFI, and GPT, this process would now be easier and allow 5+ "primary" partitions with the ability to retain the recovery partition? – Jason Jan 19 '14 at 8:11

Ok, this is written for a 500GB HDD. 4 partitions max, just like every other (bootable) hard-drive.

I tried this on 2 MacBook Pros and it works perfectly on both.

This tutorial also assumes you have OS X Lion installed.

What I want to achieve is to have OS X Lion & Windows 7 installed, with a shared space too.

  • 120 (OSX)
  • 260 (SHARED)
  • 120 (Windows)

------------Part 1/2------------

Start off by resizing Mac OS X Partition so it's at least 1GB smaller than the full disk.

To do this; go into Utilities and then into Disk Utility. Select your HDD and go to the Partition tab.

1GB is not actually needed, but it's just to be on the safe side, it'll get resized later. There needs to be 'Blank' unallocated space available.

What you originally have (factory settings):

 diskutil list


  • disk0s1 EFI (Boot) ~200MB
  • disk0s2 Mac OS X 10.7
  • disk0s4 Mac OS X Recovery

disk0s4 needs to be deleted. Go into Utilities, and load up Terminal. Type the following:

diskutil eraseVolume HFS+ Blank /dev/disk0s4

Then go into Disk Utility and delete the 'Blank' Partition. You should only have your OS X Partition and blank space.

Then check your partitions with the command 'diskutil list', you should now have:


  • disk0s1 EFI (Boot) ~200MB
  • disk0s2 Mac OS X 10.7


This part was referenced from: http://osxdaily.com/2011/06/30/deleting-the-mac-os-x-10-7-lion-recovery-hd-partition/

------------Part 2/2------------

Stretch OSX to the full available space using Disk Utility.

Load up Bootcamp Wizard, make Windows Partition 120GB whilst OSX has the remaining 380GB.

Bootcamp should be happy to start the install, but load up Disk Utility first

NOTE: On Lion 10.7.2, Bootcamp has changed a little. You need to insert the Windows 7 disk and then proceed with the installation before the Bootcamp partition will be created. When your computer restarts you need to hold down the option (alt) key and boot back into Lion, then follow the steps below:

Select the OSX Partition, and '+' another partition.

Reduce OSX to 120GB and make the new (middle) partition MS-DOS FAT, call it SHARED. That's what I'm using for now. Whilst FAT doesn't allow for any single files over 4096MB; it's also writable natively with both OS's.

It should be 260GB. Now you have:

  • 120 (OSX)
  • 260 (SHARED)
  • 120 (Windows)

According to Disk Utility, but... In reality what we have is:


  • disk0s1 EFI (Boot) ~200MB
  • disk0s2 Mac OS X 10.7
  • disk0s3 SHARED
  • disk0s4 Windows 7

Insert Windows 7 disk (if you haven't already) and then start the install sequence.

You'll notice that there's a 128MB unallocated space. Tragically you'll have to leave that unallocated.

Format the BOOTCAMP partition (only) and proceed to install Windows.

Don't mess about with deleting and merging partitions, otherwise the partition tables will be damaged.


  • You're welcome buddy, glad my method worked for you! Took me 9 solid hours of formatting and re-installing to work out. Thanks for the correction too! – HuzZz Sep 3 '11 at 3:53
  • Well, this method is not so good. It makes you delete the backup recovery HD, which is very handy to let it be there. It's just 600 MB – Timotei Oct 27 '11 at 15:49
  • Well do you see any other way round it? It's a physical restriction of a disk to have 4 partitions, this is the only possible way round it. Beggars can't be choosers. – HuzZz Jan 12 '12 at 18:17
  • 1
    Rather than formatting the shared partition in FAT or exFAT, you could use HFS+ or NTFS (depending on whether you're going to use OS X or Windows most, respectively). These filesystems are safer as well as offering better performance, at least on their native OS. If you choose HFS+, install MacDrive under Windows for write support. If you choose NTFS, install NTFS-3G (MacPorts/Fink, free) or Tuxera (faster) under OS X. – Julian Nov 13 '12 at 15:38
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    "Start off by resizing Mac OS X Partition so it's at least 1GB smaller than the full disk"--why is this step necessary? I've seen many shared-partition tutorials which don't have this step--and they still work. – yurkennis Mar 9 '15 at 6:43

Here is my recipe for a

Successful setup of OS X Lion + Bootcamp Windows 7 Ult + Data Partition

Ok, so after many, many hours I think I've finally figured out how to successfully install Mac OS X Lion with Windows 7 on a Bootcamp partition AND an 3rd data partition. Here is a screenshot of my setup on my 13" MacBook Pro as it looks at the end of the process:

Disk Utility screenshot As you can see, I have my internal 500GB hard drive partitioned the following way:

  • 120GB OS X Lion (system and apps)
  • 316GB workspace partition (user files, projects)
  • 64GB Bootcamp Windows 7 Ultimate

To make this work, I started with the standard procedure of installing OS X Lion on a single Mac OS Extended journaled (HFSJ) partition. Next I used Bootcamp Assistant to build the Bootcamp partition for Windows.

Then I did two key things:

  1. Before installing Windows on the Bootcamp partition, I first went back to Disk Utility, shrunk the OS X Lion partition, and inserted a 3rd partition Workspace_HD for all my user files. Then I restarted and installed Windows 7.

  2. After Win 7 Ultimate, the Bootcamp drivers and Office 2010 are installed and activated, I did not make any changes to any partitions. I can put whatever I want on any partition, but any effort to shrink, resize, delete, create, or modify any partition results in failure.

Any change to the partition tables after Windows is installed breaks the Bootcamp partition.

I went thru 3 broken installs of Bootcamp/Win7 to figure this out.

Again, the key to this working is creating your extra partitions AFTER you make the Bootcamp partition but BEFORE you install Windows.

I will rebuild my system for a 5th time to fully document the process with screenshots, but this time with 5 partitions: OS X Lion startup, Workspace, custom 20GB OS X Lion recovery partition, 30GB FAT32 shared Mac/Win data partition, and a Bootcamp partition with Windows 7 Ultimate.

Until then, here is a quick step by step of what I did:

  • Install OS X Lion on a single partition hard drive.
  • Run Bootcamp Assistant.
  • Download drivers for Mac and burn to CD.
  • Make 60GB Bootcamp partition for Windows.
  • When prompted for install disc, STOP installation and quit Bootcamp.
  • Launch Disk Utility. Look at the 2 partitions.
  • Shrink Mac OS X partition to 100GB.
  • Click on + to create a 3rd partition in free space.
  • Split that partition into however many other partitions you want.
  • Quit Disk Utility.
  • Insert Windows 7 installer DVD and restart Mac.
  • After the startup chime, hold down OPTION key.
  • Wait a while until the Windows 7 DVD appears and select it.
  • Mac should start up from DVD. Start installing Windows 7.
  • Continue until finished. DO NOT connect to internet.
  • Load Bootcamp drivers CD that you burned and install.
  • When finished, restart and log into Windows 7.
  • Continue installing your applications. Do activations.
  • When finished, restart, holding down the OPTION key.
  • You should now see your OS X Lion and Win 7 partitions.

OK, hope this works for you!! Good Luck!! ;-)

  • 1
    Ernie, your method sounds like what I did on my Attempt #4. I couldn't get it to work. Regarding your 5th attempt with screenshots etc, I think you'll find you won't be able to have more than 4 partitions on a single hard drive - but good luck, keep us posted. – Matt Frear Aug 29 '11 at 21:20
  • DO NOT connect to internet. -- what's reason for this remark? – yurkennis Oct 16 '13 at 18:47
  • @yurkennis, I guess because windows may download and install some wrong drivers for your mac hardware. – Dmitriy Jun 30 '14 at 11:55
  • I wonder why this answer doesn't mention the "remove OS X recovery partition" step? – yurkennis Mar 9 '15 at 6:46

I managed to get everything works like the way I want:

  • Lion, Windows 7, and two shared partition (don't ask why I need two, I do need two)
  • Lion recovery partition is intact
  • Factory-installed Lion is intact

The key of my success is moving my Boot Camp partition to the first position, as shown in this image:

When I say moving, there's no such a tool or way to move partition. I have to recreate all partitions without having to actually clean the HD and remove factory-setting Lion. As I use MBP retina, and reading from several references that Lion installer on the Mac App Store is not compatible with MBP retina, I don't want to lose it.

The steps are:

  1. Split the default Macintosh HD partition into two. Resize the first one to 120GB. This will be a Boot Camp partition later.
  2. Split the second partitions into three more partitions like the image. All partitions are in HFS+ format. The last partition is to be Macintosh HD (Lion boot partition) later.
  3. Restart MBP and reboot using Recovery partition (Cmd+R).
  4. After recovery partition is booted up, I open Disk Utility. Clone the first partition to the last partition. Just googling how to do that (eg this answer will help). Now I have two Lion partitions. Luckily, this step will create two Recovery partitions.
  5. Exit recovery mode and reboot using the just created (cloning result) Macintosh HD to make sure everything is OK.
  6. After everything is exactly like before, I reboot again using Recovery by pressing Option key, then select the second Recovery, not the first one.
  7. After recovery booted up, I open Disk Utility and remove the first partition. Then create Boot Camp partition out of it, and format it using ExtFAT so that later Windows can be installed here (need to reformat later to NTFS). This step will also remove original Lion Recover Partition.

And that's it. Then I install Windows 7 on the first partition using USB key (since MBP Retina doesn't have DVD drive). After Windows installation finish, install Boot Camp drivers, and Windows recognizes the two shared partitions above.

Since all steps are done in MBP retina with flash storage, and it's super fast, all steps only take about one hour. But I do need some time to think about the solutions.

We do have choice!

Hope it helps.

  • Thanks for the great tutorial! Will such a scenario work for Mountain Lion? – yurkennis Mar 9 '15 at 6:49
  • "After recovery booted up, I open Disk Utility and remove the first partition" -- Under Mountain Lion, I consistently get "Partition failed with the error: Couldn't unmount disk" when clicking "-" for the original OS X partition, even if I manually unmount this partition before clicking "-". However, it removes fine if I boot as usual via "Macintosh HD" partition. Am I doing something wrong? – yurkennis Mar 9 '15 at 8:13
  • At step 7, Bootcamp Assistant is unable to create a bootcamp partition: "This disk is your OS X startup disk and appears to have been partitioned by another utility". And if I start with a single OS X partition and then immediately make BootCamp Assistant create Bootcamp partition, it always appears #2 in the partition list in Disk Utility, not on top of it. – yurkennis Mar 9 '15 at 9:03

I've tried twice five times:

(as suggested by bmike, I've moved my failed attempts into a separate answer)

Attempt 1: Using Boot Camp assistant, resize OSX partition to 50Gb, Bootcamp to 200Gb, install windows. In Windows, Shrink C:, attempt to add new partition but got scared by a Windows warning message about having to convert the disk to a dynamic disk and becoming unbootable to other OSes. Aborted.

Attempt 2: Delete Bootcamp partition, starting all over again. Using Boot Camp assistant, resize OSX partition to 200Gb, Bootcamp to 50Gb, install windows. Then in OSX, use Disk Utility to shrink OSX partition to 50Gb and create a new 150Gb shared partition (exFat). Result: Windows Bootcamp partition is still visible but I can't boot it up (ie it's missing from the OS boot menu).

Attempt 3: Same as Attempt 2 but using Fat instead of exFat. No difference.

Attempt 4: During step 1, Boot Camp formats my USB stick so that I can boot off it and install Windows. So in my Mac, I fiddled with my partitions until they are how I want them: enter image description here

I can see and use the DATA partition on the Mac. So then I booted off my USB stick and installed Windows to the Bootcamp partition. So far so good. But when I boot into Windows, the Data partition is not visible. If I go into Disk Management, the space is marked "Unallocated". If I try to create a partition, I get a warning saying that Windows will convert the disk into a dynamic disk, so I'm too scared to proceed and wipe out Mac OS.

enter image description here

Windows is showing a few more partitions than the Mac does. The first 200Mb is the "GPT Protective Partition", and I think the 620Mb one is the Lion recovery partition.

Perhaps the only way to do this is to delete the Lion Recovery partition. If I convert the disk to a dynamic disk will OSX be able to boot it? Why does Windows think my shared partition is unallocated but OSX sees it as a FAT partition and can write to it?

Attempt 5:

I followed Thomas Jespersen's instructions below and started again, this time deleting the Lion Recovery partition during Windows startup, and I also followed the instructions here to prevent the creating of a 100Mb windows recovery partition. http://www.mydigitallife.info/hack-to-remove-100-mb-system-reserved-partition-when-installing-windows-7/ So now in Windows Disk Manager everything is looking fine. 4 partitions all the sizes I want them.

200 Mb GPT partition

50Gb OSX

50Gb Windows

150Gb Shared partition

But alas over in OSX I can't see my shared Windows partition. In OSX Disk Utility the partition is greyed out and if I click Verify Disk I get "Invalid BS_impBoot in boot bloc". The only option that Disk Utility gives me is to Repair Disk. I get the feeling that if I click Repair Disk it will restore the Mac Recovery partition and undo everything.

Update: I tried clicking Repair Disk and sure enough it wiped out my Windows partitions. I give up. I'm going to allocate 200Gb to Windows and store my media there.

Attempt 6: Followed HuzZz's instructions and it worked. Yay!

  • This is an amazing amount of work - thanks so much for splitting it off. I can't find any flaws in your process yet - I'm curious what is different between @ErniePena and your mac. This certainly is harder than I had thought possible. – bmike Aug 29 '11 at 21:33

Easy. Don't be afraid of the long answer.

Use BoottCamp to create a 50GB Lion and a 200GB Windows partition. Because Mac has a 200MB utility partition you will see the following when installing Windows:

200 MB Mac Utility

50Gb Lion MAC OSX

600 MB (Wierd partition created by bootcamp)

200 GB Windows BootCamp partition

These are all primary partitions, and because you can only have 4 primary partitions you may think you are stocked.

But ... When installing Windows, just delete partition 3 and 4 and create a new 50GB partition for Windows an leave 150GB free space.

After Windows is installed create a D drive with the 150 GB free space.

: Thomas

PS: Because you already did it wrong, you can try and use the Schrink partition in Windows to 50 GB but you still need to delete the weird 600 MB partition... Otherwise Windows will convert the disk to a dynamic disk (to get over the 4 primary partition limitation)... And then you can't start OSX. When you delete the weird partition you may get problems startin Windows because it changed position... U can use bcdedti.exe in a repair prompt. I guess this is not a problem on Windows 7 (not sure). This will give you 600 MB waste... but you save a reinstall.

PPS: 50GB is NOT enough for Windows and Visual Studio. When you update Windows old files are not deleted, and system restore grows and grows. Give it at least 60-80GB... you will thank me later. Starting with Win7SP1 disk wil help a bit.

  • Hi Thomas, thanks for your answer. I've tried starting again using your method (see Attempt 5) and although the partition is visible in Windows (it's exFat), I can't see it in the Mac. Any suggestions? – Matt Frear Aug 22 '11 at 21:02
  • Hi. The problem you have with seeing the shared drive in Mac OSX is properly because you formatted the shared partition with NTFS. Only FAT32 is supported on both Windows and OSX, and FAT32 is not a good file system. You can take a look at something like this: macupdate.com/app/mac/26288/ntfs-for-mac-os-x . There might be something better... I haven't tried it though. – Thomas Jespersen Aug 24 '11 at 16:01
  • OK... watch out for the NTFS-for-mac link I just sendt... it looks like a lot of people have problems with corrupted drives. Try to google "NTFS for Mac" or the other way around "HTFS for Windows". – Thomas Jespersen Aug 24 '11 at 16:32
  • @Thomas Jespersen OS X can read NTFS drives, just not write to them. It should definitely be able to see the partition. The error message "Invalid BS_impBoot in boot bloc" sounds more like there's an error in the partition table. I suspect that Windows didn't update the partition table correctly when he made the data partition. – Kris Harper Aug 24 '11 at 17:38

I recommend creating a ExFat partition which can be read and written on by both, Win and Mac

Regarding your criticism: just as Mac OS is limited to reading on the recently common Windows file systems, this problem also exists in the other direction. Win can only read from Mac OS Extended. So blame either of the players or none


Have you tried setting up your partitions first? That would be my suggestion.

Use the OS X install disk to partition your disk how you like. You can access disk Utility from an installer screen by selecting it from the Utilities menu. Then install OS X, then use boot camp to install Windows on the other partition.

As you've seen, resizing partitions once there's an OS installed can be tricky for a variety of reasons. To avoid this, just don't install anything until you've got your partitions correct.

  • 1
    That won't work. Boot camp will only install on a drive with one partition only. – Matt Frear Aug 20 '11 at 22:27
  • Ah, that's pretty silly. It seems like some people have successfully done this anyway, without the use of Bootcamp. See here and here. I'd say it's worth a shot, but it's up to you. – Kris Harper Aug 20 '11 at 23:19
  • Thanks. However I have a Macbook Air with Lion = no installation CD :-( – Matt Frear Aug 21 '11 at 10:19
  • Even more ridiculous. It looks like Apple provides a program to make a bootable partition on an external drive. There are instructions here with a download link to the assistant at the end. If you have a USB stick or external harddrve, that should work. – Kris Harper Aug 21 '11 at 16:15
  • Hi. I've updated my question with Attempt #4 but it's still not there. – Matt Frear Aug 21 '11 at 17:30

If memory serves me, the bootloader doesn't not allow for multiple partitions. Using rEFIt should allow you to do get around this restriction.

  • 1
    Can anyone confirm if rEFIt will help in this case? No votes, no comments.... – bmike Sep 1 '11 at 19:39

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