A quick tutorial on Windows partition types
A recent reader letter lamented the accidental deletion of a critical PC partition. The event rendered the machine unbootable.
It’s easy to get confused about Windows partition types. Here’s a refresher.
Partitions are, of course, the basic building block of personal computer storage devices. Adding a new drive to a system might require defining whether it’s one big partition or several smaller partitions. Typically, you then set the partitions as simple volumes and format them. (Only the boot partition/volume is set to « active. »)
These basic steps can be managed with Windows built-in Disk Management app (diskmgmt.msc), but I prefer to use a more-powerful third-party tool such as EaseUS Partition Master (free, paid; site).
Figure 1 shows the drive layout for my test Windows 10 system. It has five partitions spread over three physical drives — it’s what you might see on a heavily use desktop PC. (Note: This system was upgraded from Windows 7 to Win8.1 to Win10.)
Figure 1. The basic partition structure of a three-drive, five-partition system.
Right-clicking a drive name and selecting Properties/Volumes, shows the drive type, partition style, and other important information about a physical drive, as shown in Figure 2.
Figure 2. The Volumes tab provides basic information about a physical drive, including the number and size of partitions.
Here’s a simple breakdown of that information.
Disk number: Physical drives are automatically assigned numbers by Windows, as they’re initiated. The boot drive is almost always Disk 0. Note that the drive letter (C:, D:, etc.) is not tied to the drive number; aside from drive C:, you can usually reassign drive letters as needed.
There are, however, some exceptions. Letters A: and B: were originally reserved for floppy drives — and still are — so they’re essentially unused these days. Drives D: andE: are typically assigned automatically to optical drives, but that’s not a requirement. For example, if you have a newer system with no optical drive, and you insert a thumb drive, it’ll likely be assigned as drive D:, by default.
Bottom line: Typically, you’ll only need the disk number when using some advanced command-line tasks.
Type: On most workstations, Windows’ Disk Management app usually labels fixed drives as « Basic » and removable devices such as flash drives as « Removable. » But another two drive types are « Basic » or « Dynamic. » Simply put, Basic disks are contained on a single, physical drive, while Dynamic disks can span multiple drives — a requirement for RAID and server applications (more info).
There’s another wrinkle in Windows’ fixed versus removable status. With removable drives, clicking Properties/Polices in Windows’ Disk Management gives you two « Removal policy » options: Quick removal (the default) and Better performance (see Figure 3).
Figure 3. The properties for removable drives include safe or fastoptions.
These options don’t appear on fixed drives, but they also seem disconnected from whether the type is labeled as Basic or Removable. For example, I had an internal drive connected to the PC via a USB drive adapter. That drive was labeled « Basic, » but the properties dialog box included the Removal policy options. On the other hand, it did not include « Eject » in the right-click context menu in File Explorer.
Partition style: Most Windows-workstation drives are set to a Master Boot Record (MBR) partition style. This is the original format for PCs, but it has two significant limitations: First, it typically can’t address drives larger than 2TB. Until fairly recently, that wasn’t a big problem for most PC users. But now drives of three and four terabytes are common and — cheap. Second: MBR disks are limited to four partitions.
The Globally Unique Identifier Partition Table GPT) technology solves the size and partition-number problem, and you might see it on newer Windows 10 machines. Not only does it support truly massive drive sizes, it allows for up to 128 primary partitions. (It doesn’t, however, provide any real performance improvements.)
To boot Windows from a GPT drive, you must have a 64-bit OS and a UEFI-boot system. For more on the differences between MBR and GPT, see the comprehensive MSDN page, « Windows and GPT FAQ. »
Bottom line: In most cases, you don’t need to worry whether your original boot drive is MBR or GPT. But if you purchase a drive larger then 2TB, you’ll want to set it up with GPT.
Reserved space: This typically small partition might also be called System Reservedor just System. The reserved space is automatically created when a drive is first partitioned by Windows. It can’t be created after other partitions. OEM vendors might give this partition another name (such as SYSTEM_DRV) and make it significantly larger so it can also hold system recovery tools.
According to a TechNet article, the reserved partition usually holds the Boot Manager code and the Boot Configuration Database. It can also contain BitLocker startup files and software used for UEFI/GPT-equipped systems.
It’s possible to boot Windows without a system/reserve partition, typically by not letting Windows create in the first place. (Use a third-party partition manager to create one partition on the drive, before installing Windows.) But it’s really not worth the effort. You’re not going to gain that much free disk space.
Most important, you can’t simply delete the system partition if it already exists. As one Windows Secrets reader discovered, it will probably make your system unbootable.
The reserve partition can also cause problems when upgrading dual-boot or multi-boot systems. With multiple versions of Windows installed, the order of OS installation becomes important; newer Windows boot managers, held in the reserved partition, are often not compatible with older operating systems. For more on this, see the Feb. 12, 2015, LangaList item, « How to avoid Win7/Win8 dual-boot hassles. »
Recovery partition: Installing Windows 10 will probably result in the creation of a hidden Recovery partition. It’s used to support the Windows Recovery Environment (WinRE) — first released with Vista. WinRE can help a system recover from severe boot problems (more info), and OEM vendors might also use the recovery partition for their own rescue tools.
Although many of the WinRE functions are duplicated in the Windows recovery/rescue disc (which you undoubtedly created), it’s generally best to leave this partition in place — unless it’s taking an extraordinarily excessive amount of disk space.
Primary, Extended, and Logical partitions: Primary partitions can contain both system files and user data, and they’re typically used on the boot disk (Disk 0). Non-boot drives might be automatically set up as Extended partitions with one or moreLogical drives. Each logical drive is formatted separately and assigned its own drive letter. Again, the MBR format allows no more than four partitions on a disk. To break that limitation, one of the four must be an extended partition with one or more logical drives.
First introduced with Windows 8, Microsoft’s Storage Spaces is effectively the opposite of partitioning. The technology lets you create virtual disks pooled from multiple drives. If at some later time you need additional storage, more drives can be added to the pool. Think of this as a form of RAID.
Storage Spaces lets you set up Simple spaces with no redundancy, Mirror spaces protects against a single drive failure, and Parity spaces lets you recover from up to two faulty drives. According to the Win10 Storage Spaces overview, you can use various types of hard drives.
Sounds simple, but it has some catches. For example, when you first create a new Spaces pool, the selected drives are formatted. And you’ll need a minimum of two extradrives that can be safely wiped — your boot drive obviously can be included in a Spaces pool. However, new drives can be added later, without reformatting the original pool of drives.
The average Win10 user isn’t going to benefit from Storage Spaces. It’s really intended for keeping large amounts of data safe from local drive failures. But if you keep very large libraries of digital images or music, it might be worth a look (more info).
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