Windows 7 / Getting Started

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Choose the Right Filesystem

The filesystem is the invisible mechanism on your hard disk that is responsible for keeping track of all the data stored on the drive. Think of it as a massive table of contents, matching up each filename with its corresponding data stored somewhere on the disk surface. Windows 7 supports four hard disk filesystem types:

FAT (File Allocation Table, 16-bit)
FAT is used for all drives under 512 MB, such as small flash memory cards and floppy disks. The largest drive supported by the FAT filesystem is 2 GB.

FAT32 (File Allocation Table, 32-bit)
Designed to overcome the 2 GB partition limit with the FAT system, FAT32 is supported by every version of Windows since Windows 95 OSR2. Today, it's used mostly for flash memory cards larger than 2 GB, and on older PCs running Windows 98 and Windows Me. In addition to the support for larger drives, it also supports smaller file clusters (see the upcoming "Understanding Cluster Sizes"), so it stores information more efficiently than FAT.

exFAT (a.k.a. FAT64)
The "Extended File Allocation Table" was designed to resolve many of the shortcomings of FAT32 and to be used on drives where NTFS isn't practical, such as flash drives. exFAT is supported in Windows 7, Windows Vista SP1, and earlier versions with a free update.

NTFS (NT Filesystem)
NTFS, designed from the ground up to completely replace FAT/FAT32, is the default filesystem on all Windows 7 PCs. (Specifically, Windows 7, Vista, and XP all support NTFS version 3.1.) It offers security features like encryption and permissions, compression, and quotas. It's typically faster and more reliable than FAT/FAT32, and theoretically supports drives up to about 15 exbibytes (264 bytes) in size.

Windows 7 can only be installed on an NTFS drive, but it can read partitions formatted with FAT or FAT32. And you can add support for other filesystems with add-on software; for instance, you can read Mac OS X HFS+ drives with MacDrive.

If Windows 7 is the only operating system on your computer, all your drives should be formatted with NTFS. The only compelling reason to use another filesystem is if you have a dual-boot setup with a very old version of Windows, in which case you'd need to choose a filesystem recognized by all operating systems on your computer. Table below shows which filesystems are supported by all recent versions of Microsoft Windows.

Filesystems supported by recent versions of Windows

	FAT	FAT32	NTFS
Windows 7	✔ (data only)	✔ (data only)	✔ (v3.1)
Windows Vista	✔ (data only)	✔ (data only)	✔ (v3.1)
Windows XP	✔	✔	✔ (v3.1)
Windows Me, 98, and 95 ORS2	✔	✔
Windows NT 4.0	✔		✔ (v1.2)
Windows 95	✔

To find out which filesystem is currently being used by a particular drive on your PC, just right-click the drive in Windows Explorer and select Properties. Or, open the Disk Management utility (diskmgmt.msc) to see an overview of all of your drives.

Understanding Cluster Sizes

Clusters are the smallest units into which a hard disk's space can be divided. A hard disk formatted with the traditional FAT system, found in Windows 95 and an ancient operating system called "DOS," can have no more than 65,536 clusters on each drive or partition. This means that the larger the hard disk, the larger the size of each cluster.

The problem with large clusters is that they result in a lot of wasted disk space. Each cluster can store no more than a single file (or a part of a single file); if a file does not consume an entire cluster, the remaining space is wasted. For example, a 2 GB FAT drive would have a cluster size of 32 KB; a 1 KB file on a disk with a 32 KB cluster size will consume 32 KB of disk space; a 33 KB file on the same drive will consume 64 KB of space, and so on. The extra 31 KB left over from the 33 KB file is called slack space, and it can't be used by any other files. With thousands of files (especially those tiny shortcuts littered throughout a Windows installation), the amount of wasted slack space on a sizeable hard disk can add up to hundreds of megabytes of wasted space.

You can see how much space is wasted by any given file by right-clicking on the file icon, selecting Properties, and comparing the Size value with the Size on disk value. The same works for multiple selected files and folders; highlight all the objects in your root directory to see the total amount of wasted space on your drive. To find the current cluster size of your drive, just open the properties sheet for a small file you know will only consume a single cluster (such as a Windows Shortcut); its Size on disk will be equal to the size of one cluster.

If you want to reduce the cluster size of a drive, you'll need to reformat it. Right-click a drive in Windows Explorer or Disk Management, select Format, and choose the cluster size you want from the Allocation unit size list. The smaller Allocation unit size you specify, the less space will be wasted. For instance, the NTFS filesystem can handle more than four billion clusters. This means you could choose a cluster size of only 4 kilobytes, and still format a partition of up to 14.9 terabytes (15,259 GB) in total size.

Note that for performance reasons, it's best to stick with the default cluster size unless the slack space turns out to be a significant issue.