Super User is a question and answer site for computer enthusiasts and power users. 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

I have got my paws on a large USB drive which I'd like to use as a backup/general storage at the office. I was thinking of having two partitions one of Time Machine backup and one for general storage. As I will be using the disk for both my Linux workstation and MacBook Pro I was wondering what file system to use.

I have been reading up on old forum threads and questions here, and my understanding is that Time Machine demands a volume with HFS+ file system, meaning it would not work with ext4. Likewise HFS+ will be read on Linux, but performance-wise it would be questionable. The majority of the info I found is from 2009-2010 era, so I am wondering if there has been any changes, could someone confirm or deny these statements? or perhaps add more info on the matter...

Would it be then advisable to have one partition with HFS+ and one with ext4? I am skeptical if that would be much better... Furthermore, the disk utility tool in OSX doesn't give the option to format with Linux native, apparently it's more likely that one uses Win/OSX than Linux/OSX..

share|improve this question
I thought extended was a file system option? – Simon Sheehan Feb 22 '12 at 10:39
You mean exFAT, or ext2/3/4? THe latter is not an supplied as an option, while the former is not particularly desirable :( – posdef Feb 22 '12 at 10:41
up vote 20 down vote accepted

Linux can write to HFS+ without problems. If you really need read/write support from both OSes, then you only have one choice, namely to format as HFS+, since Time Machine won't work with others and OS X can't natively write to ext4 (see How can I mount an ext4 file system on OS X?)

I would advise you to create two partitions:

  • One HFS+ Journaled for Time Machine, so it's isolated from the partition you want to share
  • One HFS+ Non-Journaled for Linux and OS X data sharing. Linux doesn't allow writing to journaled HFS+ volumes.

Format the first one using Disk on your Mac. If you want to use ext4 for the second one, plug the disk into your Linux machine and use GParted or a similar tool to create the second ext4 partition.

share|improve this answer
thanks for the reply, I was wondering whether or not the second partition (the one for linux/osx) would better be ext4 or hfs+. I mean from what I understand both choices have drawbacks. Do you have any comments on that? – posdef Feb 22 '12 at 10:47
You won't be able to write to it from OS X when it's ext4, unless you plan using third party tools. I don't think writing speed to HFS+ from Linux would be a big issue on the other hand. – slhck Feb 22 '12 at 10:49
how about HFS+ Journaled and Linux. I read somewhere that Linux compatibility is depending on whether or not not the HFS+ volume is journaled or not (as in no joy if the HFS volume is journaled) – posdef Feb 22 '12 at 10:51
reference for the above comment: "The Linux HFS+ kernel driver has support to read and write to HFS+ non-journaled drives/partitions but only has read support of journaled HFS+. Journaling is a redundant behavior of a filesystem that helps protect against data loss. If planning to write to an HFS+ partition then drive journaling must be turned off in Mac OS X." (retrieved from Wikipedia, but referenced to a thread in Ubuntu forums) – posdef Feb 22 '12 at 10:56
Also, there are mentions of problems for partitions larger than 2 Tb: "In 2009, these drivers were diagnosed to be corrupting HFS+ drives with a capacity greater than 2 TB. Consequently, Linux distributions such as Debian and Ubuntu also stopped allowing mounting of HFS+ drives or partitions greater than 2 TB. As of February 2011, work is in progress to lift this restriction." (wikipedia) – kolen Oct 16 '13 at 9:41

Just to add to slhck's answer, formatting the partition as non-journaled was a little tricky using Disk Utility on OSX 10.7 as the option for HFS+ nonjournaled is not apparent in the formatting (erase) options.

The solution is to format it as HFS+ journaled then turn off journaling by selecting the partition then, while holding option key, open the "File" menu and select "Disable Journaling".



share|improve this answer
It seems (after trying it) that you can turn journaling on and off at any time (using the weird method of this answer), without affecting the contents of the partition. So if you like, you could turn on journaling whenever you're on a mac, as long as you remember to turn it off before ejecting (so that it mounts as read/write (instead of read only) on linux). (Too bad OSX can't do this automatically for us, with some 3rd option like "only journaled on macs (linux-friendly)"...) – Matt Jan 28 '14 at 7:59

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .