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 tech talk file systems

File Systems


This is the fourth and final installment of my series about hard drives. In part one I talked about the different physical types of hard drives and storage devices in general. In part two I explained how we measure the size of files we store on hard drives, and the speed when moving them around. In part three I talked about all the ways we connect hard drives to a computer, with pros and cons for each. In this last part I want to get a little bit more technical and talk about how to format a hard drive, and what file systems you have at your disposal.

File Systems

As you may recall from my previous post, a hard drive is just a polished disk of metal that gets magnetized with a series of ones and zeroes. But the computer needs a way to address and keep track of those ones and zeroes, and it needs to understand where one file ends and another begins. This is called a file system, and it’s in charge of providing a format for the hard drive that the computer's operating system can interact with. The file system is responsible for organizing files into a directory structure—commonly called folders—and for governing permissions on individual files and folders so that only the people who are allowed to access a file can see it. The type of file system also determines file storage efficiency (so you can fit more on a disk), and compatibility across different operating systems. Let's look at the most common file systems you’ll encounter:

FAT16 and FAT32

FAT stands for File Allocation Table, and this file system goes all the way back to DOS days. It’s not very efficient (small files tend to take up more space than they need) and it doesn't support individual permissions on files, but it is universally accepted on any device you can imagine. In fact, most thumb drives and media cards for digital cameras and music players are formatted FAT16 because it works everywhere and things like unique permissions aren’t required. A major restriction of FAT16 is that you can’t store any single file bigger than 4 GB, which is a pretty severe limitation for cameras shooting high definition video.


Even though it seems like it would be based on FAT16, ExFAT isn’t backwards compatible. Its purpose is to be cross-platform, but without the file-size restrictions of FAT16. It’s a proprietary file system that belongs to Microsoft, which means any OS that supports ExFAT has to pay a license fee to Redmond. I usually format all my thumb drives as ExFAT so I can use them to transfer large files between my Mac and PC.


NTFS was introduced in the mainstream with the release of Windows XP, although it’s actually been around since ’93 with Windows NT 3.1. It stands for New Technology File System, and it supports large file sizes, but more importantly, it supports file-level permissions, which is what gave XP the capability of allowing multiple users to use a single computer (something we take for granted today) without worrying about other people accessing their private files. NTFS is still used today in Windows computers by default. Mac computers can read from NTFS drives, but can’t natively write to them without third-party software.


HFS+ is a lot like NTFS, but it’s Mac-specific. It was introduced in Classic Mac OS, but gained popularity with the release of Mac OS X and is still used by default on all Apple-branded computers today. Like NTFS, HFS+ (which stands for Hierarchical File System Plus), handles large files and supports file-level permissions. Unfortunately, Windows PCs can’t read or write to HFS+ formatted hard drives, except for when Windows is running on a Mac through Boot Camp. When Mac OS X detects a new hard drive it automatically creates an index of all the files and their contents for quick searching through Spotlight.

Other File Systems

There are actually many, many different file systems, each with their own unique benefits and disadvantages. Linux computers typically use EXT3 or EXT4 natively, but can read and write to just about anything. Windows Server 2012 introduced ReFS which can handle individual files as large as a 16 exabytes. For comparison, every spoken word ever uttered in the history of mankind would take about 5 exabytes of storage combined.  Finally, ZFS is very promising because it natively keeps a record of all file changes, creating a kind of built-in versioning/backup system, however, it’s not widely supported.
How to format your hard drive
If you need to format a hard drive, a media card or a thumb drive, here’s how. Just be sure to format it to the correct file system for your device and your needs.


In Windows 8 hold down the [windows key] and press "x", then select "Disk Management." In Windows 7 it's a little more circuitous to get to Disk Management, but a quick way is to press [windows key] + "r" to bring up the run command, and type "diskmgmt.msc" and hit [enter].

The bottom section shows a graphical representation of any physical hard drives inside—or attached to—your computer and their partitions. You can right click on these partitions to delete, merge or reformat them.

Mac OS X

Hold down [Command] and press the [space bar] to activate Spotlight and type “Disk Utility” then click the app from the search results. A list of physical hard drives appears in the left panel, with the “logical volumes” listed under each physical hard drive. A single hard drive can contain multiple partitions, formatted to different file systems, but usually contains just one. Select the logical volume you want to format and click "Erase".


This concludes my four-part series on just about everything you need to know about hard drives and the files we store on them. The cost of storage is constantly dropping, and the computers we store our data on often aren't as valuable as the data itself. It's easy to replace a laptop, but it's very hard to bring back family photos or work documents that get lost due to data corruption or a failed hard drives. Making sure your data is in more than one location is essential.


Samuel O. Blowes, Director of IT
Samuel O. Blowes

Director of IT