Choosing Mac OS X Volume Formats

Mac OS X is designed for compatibility with non-Macintosh volume formats, so you will find that Disk Utility, the Mac OS X formatting utility, offers a wide range of formatting options. The exact formatting options for your drive will vary, depending upon factors that can include the size of the drive, the drive geometry, the size of the partition you are formatting, and previous formatting used on the drive.

The most common drive formats that you will use for your volumes are:

• Mac OS Extended Previously called HFS Plus, this is the format most familiar to Apple customers; it is used by both Mac OS X and Mac OS 9.

  Mac OS X Server 10.2.2 introduced a new Mac OS Extended file-system feature known as journaling, which helps protect the file system against power outages or unforeseen failures in server components, reducing the need for repairs. While Mac OS Extended is still supported in Mac OS X 10.4, Mac OS Extended (Journaled) is the default and is recommended for most users.

  MORE INFO

  Refer to Knowledge Base document 107249, "Mac OS X: About file system journaling."

  
  

  The original Mac OS Extended file system is case-preserving, but case-insensitive, which means if you name a file File1, the Mac OS Extended file system will retain the upper-case letter F whenever you view the file. You cannot, however, put files called file1 and File1 in the same folder because Mac OS X doesn't distinguish between the two names. In Mac OS X 10.4, Disk Utility has the ability to format volumes using case-sensitive versions of Mac OS Extended or Mac OS Extended (Journaled). Case sensitivity was designed to support developers and other specialized users. Because case sensitivity can be confusing for users, it should be used only if needed.

• Mac OS Standard (HFS, or hierarchical file system) This is an older file system that Mac OS X can access, but you can't install Mac OS X on an HFS volume. Furthermore, HFS is somewhat inefficient in its use of available storage space; Mac OS Extended allows more information to be stored on the same volume and is therefore preferred.

• UNIX File System (UFS) This format is compatible with other UNIX-like operating systems. It is case-sensitive, so you can create files called file1 and File1 in the same folder. UFS volumes are not visible in the Classic environment, so this is not an appropriate volume format if you need to use Classic. However, UFS may be preferable when developing UNIX-based applications within Mac OS X.

• MS-DOS file system (FAT, or file allocation table) This is the format used by Microsoft Windows. Files on a Windows formatted drive are usable by the Windows operating system as well as Mac OS X. Due to the physical drive geometry and other factors, the MS-DOS formatting options available in Disk Utility depend heavily upon whether the disk is currently formatted in a Windows format. Unless you have a specific need to create a partition in MS-DOS (FAT) format, you will seldom use this option.

  You can mount MS-DOS volumes in Mac OS X, but Mac OS X does not support that format for startup volumes. Mac OS X can also mount volumes in the Windows NT (NTFS) format. Disk Utility cannot create volumes in NTFS format. NTFS volumes cannot be mounted in read-write mode, but you can access files on NTFS volumes mounted read-only.

• Free space This is blank space on a drive that is not formatted specifically for any volume format. You might configure a drive with a free space partition if you need to copy files onto it from a computer running Linux.