Ask Different is a question and answer site for power users of Apple hardware and software. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

It's probably not pertinent, but I'm a Mac user since the 1980's. I freely confess that as a middle-aged dog I find it increasingly harder to keep up with the latest and greatest in available Apple technology.

I also use Windows and for the last six years or so my main desktop was a Windows XP system. I have files spread over three different HDDs on this machine.

I now have a 2011 iMac running Lion and Windows 7 and I am gradually migrating to this machine. I'd like to be able to keep applications on the internal HDD and data-- documents, photos, and so forth-- on an external HDD. I have considered buying this drive and partitioning it (half for Windows, half for Mac), but before I throw any money at this I thought maybe I should ask the wise folks here what they think of this idea.

I also have a related question. I recently upgraded to a new router, and it has a USB port, so I was thinking to attach a separate external HDD to the router and use it for Time Machine. I'm also wondering about the wisdom of this.

Thanks in advance for any helpful replies.

share|improve this question

In order to use the drive for both purposes, you would need to partition it into two. In my breakdown below, partition 1 is for moving data and partition 2 is for Time Machine, but this can be swapped around if you prefer.

I would recommend formatting the partition on which you access data on in ExFAT. It is newer than FAT and does not have the 4GB file size limit. It can be read and written to on both Mac (Snow Leopard and later) and Windows (Vista and later, XP with a supplementary download). This allows for easy transfer between both platforms.

I would read up on the formats that the router supports, as I cannot access an ExFAT drive connected to it. If that does not work, the best option for connecting from both platforms is FAT, but keep in mind that there is a 4GB file limit.

The other partition can then be formatted in the HFS+J format as Ethan mentioned in his comment.

In order to get the drive working remotely, I first set mine up on my Mac and started a backup. I then cancelled this and deleted it. I then attached it to my Airport Extreme and then browsed to it through Finder. I needed to access the drive before Time Machine would pick it up (on both my iMac and Air). I cannot say whether the router you link to will work in the same way or not. Please be aware that the way I am doing it is not recommended or supported by Apple and if you do a similar approach, you do so at your own risk.

share|improve this answer

The G-drive is targeted at professional who needs a rugged enclosure.

For the same amount of money you can get a NAS with Time Machine support. Search for names like Synology/Thecus/WD/Seagate - pick what you like/need.

For my personal needs I just have a HP microserver and put Linux on it - works really well.

share|improve this answer

Partition your disk locally first. You can't partition it while its on the network (easily). Use Disk Utility, click the name of your drive (not a partition) and go to the Partition tab. Click the + and adjust the size as you wish. Then, name it and change the format to MS-DOS (FAT). Click Apply to apply your changes.

Then, adding onto Alain's answer, here is a detailed explanation and instructions in Terminal on how to setup a network-attached storage device with Time Machine.

It's more complicated than it might seem, but here's a rundown of the steps provided by the above link:

Make sure that the network device is mounted. Then, open Finder and at the menu bar, click Go > Network. Double-click your storage device and enter any authentication details if needed.

You'll need to find the name of your computer on the network. Go to System Preferences > Sharing and make a note of what it says as "Computer Name."

Enter Terminal. You can find it in /Applications/Utilities.
Run defaults write TMShowUnsupportedNetworkVolumes 1 to allow Time Machine to work with devices that it normally doesn't.

Next, we'll need to find the MAC address of your computer. Run ifconfig en0 | grep ether

The output should look like ether XX:XX:XX:XX:XX:XX - make a note of everything after ether.

Next, we'll have to create a .sparsebundle for Time Machine. Read this carefully, as this is a pivotal step in the setup process.

Still in Terminal, run hdiutil create -size 100g -fs HFS+J -volname "Time Machine" NAME_XXXXXXXXXXXX.sparsebundle - where NAME is the name of your computer (all spaces will be dashes) and the X's are your MAC address without colons.

Also, make sure that the -size argument is the space you want to create for your Time Machine. This will make the partition in HFS+J however large you want. In this particular command example, we have created a 100 GB partition for Time Machine.

You can replace -size 100g with anything you want ( 50g, 150g, even OVER 9000g [but only if your NAS has this much capacity])

Next, run rsync -aE NAME_XXXXXXXXXXXX.sparsebundle /Volumes/DRIVE/. - where DRIVE is the name of your storage drive. Remember that NAME is your computer name with dashes and the X's are your MAC address without colons.

You can also simply type rsync -aE NAME_XXXXXXXXXXXX.sparsebundle and drag in your network drive icon from Finder; it'll automatically enter its name after. This step might take a few moments. Wait for it to finish; you'll know when it prints Your-Mac-Name:~ Username$ again.

Final Terminal command: rm -rf NAME_XXXXXXXXXXXX.sparsebundle to remove the copy of the .sparsebundle from your computer. After this, you can close Terminal (whew).

You can start backing up as normal now. Go to System Preferences > Time Machine and click Choose Backup Disk... and select your network drive.

Although it will show the drive's full capacity, Time Machine will be limited to the size specified in the step where you ran hdiutil create by the -size argument.

Time Machine will start backing up.

share|improve this answer
up vote 0 down vote accepted

In case someone else is searching for answers to the same question, I thought I should leave a record of what I ended up doing.

I got a Synology DS212j NAS and put a couple of 2TB Western Digital Red drives in it.

I can back up my Apple computers on the OS X and Windows 7 partitions since the Synology NAS supports both Time Machine and backup from Windows (using the software supplied by Synology with the NAS).

In late 2012/early 2013 the total cost was around $450, including shipping.

share|improve this answer

Format as FAT32 and it can be read by both Windows and Mac OS X. I do not know if Time Machine works with FAT32 as it stores less details with the file.

share|improve this answer
Time Machine only works with their HFS+J file system, and will not work with FAT32. It can be used by Mac for file transfer, however. – Ethan Lee Nov 16 '12 at 5:26

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.