Mac OS Extended Format: Volume and File Limits

Maximum number of volumes 21 (refer to Note 2)

Maximum volume size 2 terabytes

Maximum file size 2 terabytes (refer to Note 3)

Maximum data fork size 2 terabytes (refer to Note 4)

Maximum resource fork size 16 megabytes (refer to Note 5)

Maximum number of files more than 2 billion (refer to Note1)

Maximum number of files/folders in a folder 32,767

Notes:

1) The actual number of files that can be stored on an HFS Plus volume depends on the size of the volume and the size files. For example, a 4 GB HFS Plus volume with the default block size of 4K, will have one million available blocks. Thus the volume could hold up to a million small files or fewer larger ones. A larger volume with the same default block size could hold proportionately more files.

2) At system boot, the event queue for the Finder can accept 20 volumes plus the startup volume. Once the computer has completed the boot process, you may use a disk utility to mount as many additional volumes as there are available file control blocks. This number is variable depending upon how many applications are running, files open, or other operating system processes which require file control blocks.

3) Under Mac OS 9. Mac OS 8.x only supports file sizes of up to 2 GB in size.

4) Mac OS 9 with Mac OS Extended savvy applications can access a fork this size. Mac OS 8.x and Mac OS 9 with applications using the standard HFS APIs can access forks up to 2 GB in size. It not possible to access any data in a fork larger than 2 GB without using the Mac OS Extended APIs.

5) This limit is imposed by the Resource Manager.