HFS Plus - History


HFS+ was introduced with the January 19, 1998 release of Mac OS 8.1. However, its first appearance, as a beta filesystem, was in the never-released Copland OS betas.

With the release of the 10.2.2 update on November 11, 2002, Apple added optional journaling features to HFS Plus for improved data reliability. These features were easily accessible in OS X Server, but only accessible through the command line in the standard desktop client. With OS X v10.3, all HFS Plus volumes on all Macs are set to be journaled by default. Within the system, an HFS Plus volume with a journal is identified as HFSJ.

10.3 also introduced another version of HFS Plus called HFSX. HFSX volumes are almost identical to HFS Plus volumes, except that they are never surrounded by the HFS Wrapper that is typical of HFS Plus volumes and they optionally support case sensitivity for file and folder names. HFSX volumes can be recognized by two entries in the Volume Header, a value of HX in the signature field and 5 in the version field.

Additionally, OS X 10.3 marked Apple's adoption of Unicode 3.2 decomposition, superseding the Unicode 2.1 decomposition used previously. This change has caused problems for developers writing software for OS X.

With 10.4, Apple added support for Inline Attribute Data records, something that had been a part of the OS X implementation of HFS Plus since at least 10.0, but always marked as "reserved for future use". Until the release of OS X Server 10.4, HFS Plus supported only the standard UNIX file system permissions, however 10.4 introduced support for access control list-based file security, which provides a richer mechanism to define file permissions and is also designed to be fully compatible with the file permission models on other platforms such as Microsoft Windows XP and Windows Server 2003.

In OS X Leopard 10.5, folder hard-linking was added as a fundamental part of Time Machine.

In OS X Snow Leopard 10.6, file system compression was added, which uses extended attributes to store the compressed data. Because of this, the compression is not always completely transparent when using non-Apple APIs.

In OS X Lion 10.7, file system encryption (known as FileVault 2) was added. This encryption is backed by a logical disk management system known as Core Storage. Core Storage allows for completely transparent encryption, as well as smooth transitioning between encrypted and decrypted states.

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