Dual partition a USB drive for Time Machine and Windows

2009 February 17

I just picked up a Western Digital 1 TB Element hard drive for under $100 from Dell SB. As a hedge against data loss, I’m using it as an inclusive backup for my Macbook (via Time Machine) as well as some important media files on my Windows/Ubuntu box.

There are two reasons I want to partition this drive. One, Time Machine has no feature that allows you to bound the size of the backups. Therefore, it will keep adding incremental backups without removing older data until it runs out of room on whatever drive you are using. Considering I only have a 160 GB hard drive in my Macbook; wasting 1 TB of space is pointless, and partitioning a portion of the free space for Time Machine allows it to be “bounded.” Secondly, by partitioning the drive with two file formats, I can easily attach the drive to my network (via Airport Extreme, for example) and have it be accessible from all my computers. Therefore, simple Windows backups using SyncBack can be done using the same disk as no-touch backups using Apple’s Time Machine.

So how do you set up two partitions on an external USB drive– one for Time Machine and one for using with a Windows box?


    1.) Plug your USB external hard drive into your Mac.

    2.) Open Apple’s “Disk Utility” — this can be found in the Utilities folders within the Applications directory.

    3.) On the left hand side, you will see the hard drive you wish to partition — you will likely see the manufacturer name (HD, not necessarily enclosure) — match the manufacturer and size. Select this drive (the top level, not any sublevels within the drive).

    4.) Select the “Partition” tab on the top of the right side of the utility window.

    5.) In the “Partition” tab select the number of partitions that you want from the ‘Volume Scheme’ drop-down menu. If you are planning on using a two-partition scheme like me (one for Mac, one for Windows), select “2 partitions.”

    6.) Select one of the partitions by clicking on one of the “boxes” underneath the dropdown menu. They will likely be named “Untitled X.” When a partition is selected it will be bounded by a blue border and you will notice that both “Name” and “Format” are available.

    7.) Start with your Mac (in my case, Time Machine) partition. Select a name, size, and choose either Mac OS Extended (Journaled) for a partition that you will use with Time Machine or use as a boot volume. Select Mac OS Extended (No Journaling) if you wish to use this partition for Mac media or data storage.

    8.) Select the other partition by clicking on it. For a Windows partition, select “FAT” from the drop-down menu.* The name is not case-sensitive (i.e., must be in all CAPS) and cannot contain spaces. I typically will name this “WINEXT” or “WDWIN.” Something short and sweet in case you need to browse to it through a shell.

    9.) Select each additional partition (if any) and then name and set the format.

    10.) Click “Apply.”

Voila! You now have a drive that Time Machine can use for Macbook backups, but you also have a partition for media/data file storage on your other boxes as well!

*NOTE: Some people have e-mailed and asked “why FAT? NTFS is more awesomer!” Well, I agree that NTFS is the better file standard; however, as of 10.6.1, OS X still did not have the capability to write to NTFS drives; so FAT is the preferred solution here because it would allow you to write/edit the secondary partition from your Mac if needed.

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16 Responses leave one →
  1. 2009 April 15

    Thanks! This was exactly what I was looking for. Finally going to pick up an external for Time Machine, but I wasn’t sure if I could partition it off and use some of the space for my ever growing media collection. This explanation was on the mark.

  2. 2009 July 1
    Jesse Eichhorn permalink

    Great instructions, thanks for the help!

  3. 2009 July 7
    Cecil Hudgins permalink

    Great post….I spend most of last weekend trying to figure out how to use a Seagate 1TB external USB drive to backup my iMac and two windows machines connected via Airport Extreme. I finally partioned a 400GB WD drive (200 as Mac OS Extended (Journaled) and 200 as Fat 32) but currently have it connected to the iMac. How can I attach a drive like you describe and see it on the Airport by both the iMac and Windows machines? I am having no luck in this area. The folks at Seagate said I would have to purchase a Network drive for this to work.
    Thanks for your help.

  4. 2009 July 12
    Colin permalink


    You should be able to see the drive on the iMac by using Finder and then Go -> Network -> “Insert your Airport Name.” Type password and it should allow you the option to click and mount the volume.

    In Windows, you merely have to make sure network volumes are enabled and it will show up in Explorer (below all your other Windows, FAT drives).

  5. 2009 September 4
    shak permalink

    hello there, i tried doing exactly what you did , but when i went to the format select drop down menu there was no ‘fat’, why is this?

  6. 2009 November 3
    Paul permalink

    Thanks for the instructions.

    @shak Make sure you erase you old partition, and then create 2 partitions. If you did that I don’t know how to help. GL

  7. 2011 January 11
    Paul Cunningham permalink

    Dear Colin,

    Great instructions–Thanks! Say, would it be possible to created three partitions (one for storage, and two for Time Machine backups) and use the same HD and Time Machine to backup up two Macs? I would like to use one HD to back up my MBP and MBA using Time Machine.


  8. 2011 January 11
    Colin permalink


    Yes, that’s very easy, in fact, I’m rocking that setup right now. In Disk Utility, set up a three partition scheme (two Mac OS Extended partitions, one whatever you want for storage).

    Click on the Time Machine icon in the status bar (or go through System Preferences), click “Open Time Machine Preferences” and select one of the partitions when your USB drive is plugged into the MBP and the other one when you are connected to the MBA. If you own an Airport Extreme, you can even plug the drive into the back of the router, access the partitions in Finder, and go into Time Machine Preferences and backup that way.

    HOWEVER, you don’t even need to do this. You can back up two Macs on the same drive (or even same partition) because the software will create a different sparebundle (backup file) for each system. The advantage to partitioning is that one backup file (say you use your MBA way more than your MBP) won’t grow too large and crowd the drive.



  9. 2011 January 12
    Paul permalink


    Great– that sounds very straight forward (and only four clicks away from backing up).



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  11. 2011 May 24

    Great info, to the point and simple.

  12. 2011 September 5
    Reg permalink

    I have the MiniMax 2TB drive with 1.7 TB partition for MAC OS (journaled) and 300 GB for Windows with exFAT format (IMac OS X don’t give me other choices than exFAT).
    I would prefer FAT32 or anything that Windows XP or Vista can see. Windows XP/Parallels doesn’t recognize the 300GB drive and neither my other PC with Vista. I downloaded Iomega FAT32 Formatter but it doesn’t see the drive therefore no luck with this.

    Can you please help?

  13. 2011 November 10
    Wesly permalink

    The Same. Thank for the solution

  14. 2012 March 31
    JAD permalink

    Thank you very much for the great instructions. have been searching for this for some time

  15. 2013 July 27
    PCguy permalink

    Yes – thank you for these instructions. It’s just what we needed to get Time Machine setup on our 1TB external drive – half for Time Machine and the other half for dragging and dropping files across various other OS’s. :)

  16. 2016 April 13
    AnnaB permalink

    Super Helpful! Thank you!

    For partitioning exactly the way you have outlined, it seems easiest to do it on the MAC, vs partitioning on the PC. But we all know that Macs are easier! :P

    Thanks again!

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