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Best Disk Format for External Storage Devices (USB Keys, Hard Drives etc.)

22nd March 2017 Digital Asset Management

At Image Science, we deal with files and storage devices all day every day. 

In recent years, most files have begun to arrive electronically and we have a fast and reliable file upload tool you can use to send us files.  However, we also generate large files here as part of our scanning service, and thanks to the pathetic state of what passes as internet in this country, a lot of people do still use external hard drives and of course USB keys to share files with us.

So the question then becomes - how best to do this?  What is the best modern format to use to reliably store and transfer files between systems - whatever operating system they may be running, be it PC, Mac, or Linux?

This is in fact more relevant a question in recent times than years previous as there's a strong momentum back to PCs from Macs of late! Image Science is a Windows house, because Windows printer drivers and colour management have proven vastly more reliable over the last 15 years than the ever changing Mac system. We do have software here to read Mac formatted disks if necessary, but it's never as easy and reliable as a properly formatted external drive.

The Goals

For the purposes of this article, we want to format our external drives to achieve the following things (in this order of importance):

  • Platform Cross Compatibility (with PC and Mac friendliness at a minimum
  • No File/Filename Size limits
  • Reliability

What Not To Use -> HFS/NTFS

The first thing we can easily do is rule out using HFS/+ - this is a Mac only format and requires, at best, custom software to read on other platforms. 

NTFS is also similarly easily ruled out as without custom software, Macs can read from, but can't write to, NTFS formatted drives.

Of course, you may be setting up an external hard drive purely for your own backup purposes, in which case using the best (i.e. most reliable) operating system native format makes the most sense (HFS on Mac, NTFS on Windows).  But that's another article really!

Thus, if, and only if, you are 100% sure you will only ever use  your device with a Mac, you can go ahead and use HFS.  And because it is a journalled file system, it's a robust and reliable file system.  Ditto NTFS in the Windows world.  And in the Linux world, there are lots of choices, with ext4 still being the modern default.

However, most external devices are used specifically to share files, so which format should you use for that?

Best Format for Sharing Files

The short answer is: use exFAT for all external storage devices you will be using to share files.

The long answer is the same - just with reasons!

FAT32 and exFAT are the remaining options you're given once you rule out the more 'native' file systems as above.  These are less robust file systems - so you need to take more care when e.g. ejecting your external media.  As long as you do that properly, every time, you should have no issues.

FAT32 is really the most compatible format of all (and the default format USB keys are formatted with).

Pretty much everything will read a FAT32 drive - but it is very old at this point, and has annoying limitations - and the most likely one you're going to hit is a maximum file size limitation of 4GB.  (And a maximum partition size of 8TB).  If you're sure you can live with these limitations then you're fine to use FAT32.  But digital images, especially working files with lots of layers, can soon exceed this limit.

exFAT is a more modern (2006+) FAT based file system designed to remove these limitations.  There's no real limit to the file (or filename) size on an exFAT drive.  Any vaguely modern version of Windows, Mac OSX and Linux can read exFAT drives simply. 

exFAT should be your default choice for all external storage you plan to use for sharing files.