File System and Partition Explained: How to Take Control of Your Storage

You might have never heard of the file system, but when you use a computer or any device that stores something, you have to deal with one. The same can be said about a disc partition.

This post will explain those in simple terms and help you create or format a partition on a storage device using an appropriate file system on a Mac or Windows computer.

Dong’s note: I first published part of this post on March 20, 2018, and updated it on June 23, 2020, with a significant amount of additional relevant information based on requests and questions from readers.

What is a partition

To state the obvious, we’re talking about digital storage here.

A partition is a portion or region of a storage device that users can manage independently. Once formatted using a file system—more below—a partition is now available to the operating system as a volume.

For example, in Windows, each drive letter you see (like C: or D:) represents a volume (partition).

Partition vs. volume vs. drive vs. disc vs. disk

It’s a bit of a mess regarding digital storage terminologies. That said, here’s the breakdown:

First and foremost, we have a physical storage device often referred to as a drive—like a hard drive (HDD) or a solid-state drive (SSD). But it can also be called a disc, or a disk.

That said, “disk” and “disc” refer to the same thing; it’s always the physical device that holds your data. “Drive,” on the other hand, is a bit more complicated. Hold that thought!

SSD vs. HDD: Everything you need to know about fast storage

A disc comes with unallocated space, which can be turned into a partition or partitions. In the raw state, a partition is sometimes called a volume.

Once formatted (no longer “raw”,) it can now be referred to as a drive, which is why we have the drive letters within the Windows operating system, as mentioned above.

So, again, “drive” is where it gets confusing. That’s because the term is used to call both a formatted volume—a common yet intangible concept—and a physical storage device that you can hold in your hand. Here’s a recap:

• A tangible physical storage device is called a drive, a disk, or a disc.
• An intangible (logical) storage unit on a computer is called a drive, a volume, or a partition.

One thing is significant, though: out of a physical disk, you can create one or multiple partitions.

To make it a bit easier to grasp, a partition is a walled-off section of that property if you imagine a hard drive as a warehouse. You can divide a warehouse into multiple parts to store different product types or use the whole place as one large unit.

Of course, on a disc, you don’t physically divide its storage space into smaller areas. Instead, you use software to divide its digital storage space into different portions via partitioning. And that brings us to partition types.

Popular partition types

Again, a brand-new disc generally comes with unallocated space. You first need to partition it using one of the two popular partition types: GUID Partition Table (GPT) and Master Book Record (MBR).

Both are how an operating system organizes information on a storage device.

GUID Partition Table (GPT)

GPT is a modern partition scheme that has become popular since 2010. Eventually, it will replace MBR entirely. It uses globally unique identifiers (GUIDs) to map out the partition tables on a storage device.

That said, if you buy a computer released in the past decade, chances are it uses the GPT partition type. In fact, you can safely forget about MBR unless you’re a geek.

The GPT type can handle up to 128 partitions on a single disc. Each GPT partition can hold up to 9.4 zettabytes of data, that’s 9.4 billion TB.

All macOS versions use GPT, and starting with Windows 8, Microsoft supports GPT as the boot partition type.

Note: To use a GPT partition as a boot volume, the computer’s motherboard must use a modern pre-OS low-level system called “Unified Extensible Firmware Interface” (UEFI). That’s all you need to remember. Additionally, it must use an operating system with a 64-bit architecture. A 32-bit OS can only address up to slightly less than 2.2TB in a single storage volume (partition).

Master Boot Record (MBR)

MBR is an old partition scheme first available in MS-DOS. It’s still compatible with modern computers, including the latest version of Windows 10.

Almost all existing computer platforms can read and write MBR partition types, but only Windows can use it as a boot volume. In other words, you can’t install macOS on an MBR partition.

Note: To use an MBR disc as a boot drive, the computer’s motherboard must support the old Basic Output Input System (BIOS). Most new UEFI-ready motherboards support this system for backward compatibility and refer to it as the “Legacy” boot type. Again, that’s all you need to remember.

MBR’s major shortcomings

Quite ancient, the MBR partition type has many limitations compared to GPT. The deal-breaker is that MBR can handle a maximum partition size slightly shy of 2.2 terabytes (TB), or 4.7 billion times less than GPT.

So if you use MBR on a storage device larger than 2.2TB—most hard drives and SSDs have higher capacities these days—you’ll need to create multiple partitions on it.

Extra: Primary partition vs. extended partition

Also, MBR has two partition flavors: Primary and extended. Both can hold data, but only the former can be used to boot an operating system.

MBR partition type allows for up to four primary partitions or three primaries and one extended partition. The only good thing about an extended partition is that you can subdivide it into multiple volumes.

On a Windows computer, the extended partition on a disk will be shown in a different color from the primary one—again, GPT can handle up to 28 of them. Nowadays, other than backward compatibility, there’s no need for extended partitions.

Again, Master Boot Record is so old, so you might not run into it. What you definitely will run into, no matter if you use GPT or MBR, is the file systems.

Extra: Active partition and drive cloning

When you use an MBR drive with multiple primary partitions, the partition that holds the boot information must be marked as “Active” before the drive can boot.

It’s important to note that sometimes this partition may not be the one that holds the operating system or even the one that’s categorized as “boot.” Instead, it’s the one classified as a “system.”

Making a drive bootable (such as when installing an operating system) includes marking the relevant partition active. However, if you clone an MBR drive, you might need to manually figure out the correct partition and mark it as active on the replacement drive before it can boot.

What is a file system?

A file system (or FS) is necessary to organize data that resides on a storage device. Without an FS, your computer won’t know where a document or a picture is on its internal drive to retrieve it upon your command.

If the partition is a walled-off section of a warehouse, the file system is how goods and merchandise are organized.

You must create a partition and apply a file system on a new internal hard drive or solid-state drive before you can use it. But many portable drives come with a ready-to-use partition right out of the box. In that case, you can also change it if need be.

You do this by formatting it. Knowing how to format a disc into a particular FS can come in handy. For example, you can format a Windows-based drive into one that works for a Mac and vice versa.

Popular file systems: NTFS vs. HFS+ vs. exFAT vs. others

There are many different file systems, and I mention only those relevant to the Windows and Mac platforms. If you use any other platforms, such as Linux, you’re likely an advanced user who needs no explanation on file systems.

Mac-only file systems

These are file systems that only macOS can read and write. They can also apply to the boot drive that holds the operating system on specific macOS versions.

• APFS—or Apple File System—is the default FS for macOS High Sierra (10.13) and later. Legacy MacOS versions (10.11 and earlier) cannot read APFS. Only macOS Sierra (10.12) can read APFS, though it uses HFS+.
• Mac OS Extended (Journaled) (a.k.a HFS+) is the default FS of macOS version 10.12 and earlier. While newer macOS (10.13 and later) can read HFS+, you can’t use this file system on the boot drive to hold the operating system.

Mac file systems have two attributes:

• Case sensitive allows you to name files with the same name but different letter cases (i.e., MyFile.txt vs. myfile.txt).
• Encrypted means data stored on the drive can be encrypted; use this if you intend to store sensitive data.

So, for example, if you want to use the HFS+ file system with the support for case sensitivity and encryption, then format your drive using Mac OS Extended (Case-sensitive, Journaled, Encrypted).

Neutral file systems

The following are neutral file systems that work on both Windows and macOS. Specifically, if you have a drive formatted using one of these, you can connect it to a Windows or Mac computer to view and edit its content.

In most cases, they are not suitable as the file system for the boot drive. Initially, these were file systems for older versions of Microsoft’s operating systems (MS-DOS and Windows), later supported by other platforms for file exchanging purposes.

• FAT—or File Allocation Table—is an ancient file system that was first introduced in MS-DOS (pre-Windows). FAT has a file size limit of about 2GB.
• FAT32 is an improved version of FAT and has a max file size of about 4GB.
• exFAT is an enhanced version of FAT32 with a huge file size limit. This FS is an excellent choice if you use the drive to transfer data back and forth between Windows and Mac.

Windows-only file system

Modern Windows operating systems (Windows 7, 8, and 10) share one NTFS file system.

• NTFS—or New Technology File System—was first introduced with Windows NT back in 1993 and has been the default FS for all NT-based Windows since (from Windows 2000 to Windows 10). NTFS has improved over the years, with each new version backward compatible with older ones.

By the way, this article shows in detail how Microsft’s file systems differ.

How to format a drive

To format a disc, you first need to create a partition or partitions. If your drive has no existing partition, formatting will automatically create a single partition that uses up all of its continuous unallocated space.

You can manually create multiple partitions on a disk before formatting. Conversely, you can shrink an existing volume to create unallocated space, out of which you can make another partition.

Things to keep in mind before formatting a drive

Before doing the drive format, though, let’s recap which file system to use.

If the drive you’re about to format will hold an operating system, then make sure you apply the default FS for the OS. Specifically:

• For Windows, pick NTFS
• If you use macOS 10.2 or earlier, use Mac OS Extended (HFS+)
• For macOS 10.13 or later, choose APFS.

In most cases, you probably format a disc used only to store data, like a secondary internal drive, a thumb drive, or a portable drive. If so, the following are the available file systems of choice:

• If you use only Mac computers, then pick Mac OS Extended
• For Windows-only use, choose NTFS
• In a mixed Windows and Mac environment, exFAT is the best option.

Note: Though exFAT works with Macs, it does not support Time Machine backup. Formatting a drive erases all of its content for good.

How to format a drive on a Windows computer: The Disk Management tool

There are many ways to format a drive in Windows 10, but the easiest way is to use the OS’s built-in Disk Management tool.

But first, make sure you connect the drive to the computer. Use the SATA connection or an M.2 slot if it’s an internal drive. If it’s an external one, use a USB or Thunderbolt port.

1. Right-click on the Start button to open the Windows X menu. (Alternatively, you can use the Windows + X keyboard shortcut.)

2. On the menu that pops up, click on Disk Management.

The tool launches and displays all available discs of your computer. They appear as horizontal bars, each representing a physical disc. Within each bar, you’ll see different sections, and each represents a volume—if you notice a letter (like C: or D:) within a bar, they are the drive letters you’ll see within Windows Explorer.

3. Pick the bar of the disc you want to work with and right-click on it to bring up a context-based menu that, among other things, allows you to manage the volumes however you like.

Windows 10’s relevant commands to work storage devices

These commands are items on the context-based menu that pops up when you right-click on a drive.

Commands for an unallocated space

• Create a New Simple Volume: This is how you create a new (simple) partition. You can pick the partition size or accept the default value, which is the entire unallocated space.
• Create Spanned/Striped/Mirrored Volume: This allows you to use multiple disks as a single volume in a RAID setup.

Commands for an existing volume

• Extend Volume…: Make the existing volume take over the unallocated space next to it.
• Shrink Volume…: Resize an existing volume to make it smaller so that you’ll have some unallocated space on the right of it, which you can turn into another volume.
• Delete Volume..: Turn the existing volume into unallocated space.
• Format…: This allows you to pick the file system to use after the formatting process. You’ll also be able to choose a label (a name) for the volume.
• Change Drive Letter and Path: This allows you to remove a drive letter from a volume, effectively causing it to disappear from Windows Explorer or pick a new letter for it.

There are more things you can do with Disk Management, and they are all self-explanatory.

How to format a drive on a Mac computer: The Disk Utility tool

The Disk Utility tool is the Mac equivalent of the Disk Management tool in Windows. It’s a lot more straightforward. That said, here is how you handle a disk on a Mac.

1. Connect the drive to your Mac.

2. Run Disk Utility (search for “Disk Utility” using Spotlight located at the top-right corner)

3a. To create a single partition: Click on the disk you want to format, then on Erase.

Pick the Name and the Format (file system) of your liking, and click on Erase. Wait a few seconds for the process to complete, and that’s it!

3b. To create multiple partitions, Click on the disk you want to work with, then on Partition.

Click on the Plus (+) sign to create as many partitions as you wish. Or use the Minus (-) to reduce the number.

Select the Name and Format (file system) for each partition, then click Apply. Mission accomplished.

Note that I used macOS Mojave (10.14) for the screenshots. If you operate a different version of the Mac OS, the steps and the interface might be slightly different, but the process is essentially the same.

The takeaway

File systems, volumes, drives, discs, etc., are low-level hardware and software—they are the nuts and bolts under a car’s hood.

You don’t usually need to know them, but having a good understanding of these concepts is required if you want to get the most out of your system, including building or fixing one.