File System and Partition Explained: Take Control of Your Storage

Hand Grapping on a Hard Drive
This is a laptop internal 2.5-inch laptop hard drive, a typical physical digital storage device.

You might have never heard of file systems, but when you use a computer or any devices that store something for that matter, you have to deal with one. The same can be said about disc partitions.

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.

What is a partition

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

A partition is a portion, or a 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).

This PC Folder Content
Here’s a typical view of the “This PC” folder on a Windows 10 computer. Note the drive letters. These volumes can be all of one physical storage device or four different ones.

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

It’s a bit of a mess when it comes to digital storage terminologies. That said here’s the lowdown:

First and foremost, we have a physical storage device that’s 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, 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.)

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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, it can now be referred to as a drive, which is why, within the Windows operating system, we have the drive letters, 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 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, if you imagine a hard drive as a warehouse, then a partition is a walled-off section of that property. You can divide a warehouse into multiple parts to store different types of products, or you can 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 a task call partitioning. And that brings us to partition types.

A brand new disc generally comes with unallocated space. To use it, 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 modem 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, that’s 9.4 billion TB, of data.

All macOS versions use GPT, and starting with Windows 8, Microsoft supports GPT as 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.

Master Boot Record (MBR)

MBR is an old partition scheme that was first available in MS-DOS. It’s still working with modem 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 this type 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 a lot of limitations compared to GPT. The deal-breaker is the fact it can handle the maximum partition size of just 2 terabytes (TB) or 4.7 billion times lesser than GPT.

So if you use MBR on a storage device that’s larger than 2 TB — 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 up to three primaries and one extended partition. The only good thing about an extended partition is the fact you can sub-divide 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 — gain, GPT can handle up to 28 of them. Generally, nowadays, other than backward compatibility, there’s no need for extended partition anymore.

Again, Master Boot Record is so old, so chances are 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 that has multiple primary partitions, the partition that holds the boot information must be marked as “Active” before the drive can boot.

Active Partition
Note the active partition (the first one) on this Disk 0. In this case, the partition that holds the operating system and is categorized as “Boot” is not supposed to be the active one.

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

During the process of making a drive bootable (i.e., installing the operating system,) the relevant partition will be marked active automatically. 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 for the organization of 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.

Alxum M 2 Enclosure 10
You can quickly add an internal drive to a computer via an adapter.

When you buy a new internal hard drive or a solid-state drive, you generally need to create a partition and apply a file system to it. An external storage device, like these portable drives, generally comes with a ready-to-use partition right out of the box. But you can change that to fit your needs.

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.

There are many different file systems, and I mention here 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 explaining on file systems.

Mac-only file systems

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

The list of The Disk Utility application (for Mac) gives you a lot of file system options to format a drive into.
  • APFS — or Apple File System — is the default FS for macOS High Sierra (10.13) and later. Note that legacy MacOS versions (10.11 and earlier) cannot read APFS at all. 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 of 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 on the drive.

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 the neutral file systems that will work on both Windows and macOS. In most cases, they are not suitable as the FS for the boot drive. Initially, these are file systems for older versions of Microsoft’s operating systems (MS-DOS and Windows), which later get supported by other platforms for file exchanging purposes.

  • FAT — or File Allocation Table — is an ancient file system first introduced back in MS-DOS (pre-Windows) time. FAT has a file size limit of about 2GB.
  • FAT32 is an improved version of FAT and have the 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 file system called NTFS.

  • 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 being backward compatible with older ones.

By the way, this article shows in detail how Microsft’s file systems are different from one another.

How to format a drive

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

To have multiple partition on a disk, you can manually create them before formatting. Conversely, you can also shrink an existing volume to create unallocated space, out of which you can create another partition.

Things to keep in mind before formatting a drive

Before doing the format of a drive, though, let’s recapitulate on 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 you will use on it. 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, though, you probably format a disc that’s used only to store data, like a secondary internal drive, a thumb drive, or a portable drive. In this case, the following are the general 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: exFAT, though works with Macs, will not support Time Machine backup. Also, formatting a drive will erase 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 handiest way is to use the OS’s built-in Disk Management tool.

Windows X Menu
The handy Windows X menu where you can quickly find Disk Management.

But first, make sure you connect the drive in question into the computer. If it’s an internal drive, use the SATA connection or an M.2 slot. If it’s an external one, use USB or Thunderbolt.

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

Disk Management
The interface of Windows 10’s Disk Management utility.

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

The tool launch 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 each represent a volume. If you see 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

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.
Disk Management Unallocated Menu
If you right-click on an unallocated area on a disk, you’ll get a different context-based menu which allows you to create a new volume (partition).
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 pick 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.
Disk Management Volume Menu
The context-based menu when you right click on an existing volume allows you to do many relevant tasks to the disk.

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 simple. That said, here are how you handle a disk on a Mac.

Disk Utility
The Disk Utility is a handy storage manager on a Mac, note the list of connected disks.

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.

Disk Utility Earase a Drive
Steps to format a portable drive into a new file system on a Mac.

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.

Pick the Name and Format (file system) for each of the partitions, and then click on Apply. Mission accomplished.

Disk Utility Partition a Drive

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

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 and relevant information, based on requests and questions from readers.

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