Veritas 5.0.1 Installation Guide, HP-UX 11i v3, First Edition, November 2009

VxFS Features
VxFS supports the following features:
• Extent-Based Allocation
An extent is defined as one or more adjacent blocks of data within the file system. VxFS
allocates storage in groups of extents rather than a block at a time, thereby resulting in faster
read-write operations.
• Extent Attributes
Extent attributes are the extent allocation policies associated with a file. VxFS allocates disk
space to files in groups of one or more extents. VxFS enables applications to control extent
allocation.
The setext and getext commands enable the administrator to set or view extent attributes
associated with a file, as well as to preallocate space for a file.
• Fast File System Recovery
Most file systems rely on full structural verification by the fsck utility as the only means
to recover from a system failure. For large disk configurations, this involves a time-consuming
process of checking the entire structure, verifying that the file system is intact, and correcting
any inconsistencies.
VxFS reduces system failure recovery time by tracking file system activity in the VxFS intent
log. This feature records pending changes to the file system structure in a circular intent log.
• Access Control Lists (ACLs)
An Access Control List (ACL) stores a series of entries that identify specific users or groups,
and their access privileges for a directory or file.
• Online Administration
A VxFS file system can be defragmented and resized while it remains online and available
to users. The online administrations operations supported are backup, resizing, and
defragmentation.
• File Snapshot
VxFS provides online data backup using the snapshot feature. An image of a mounted file
system instantly becomes an exact read-only copy of the file system at a specific point in
time. The original file system is called the snapped file system and the copy is called the
snapshot.
• Expanded Application Interface
VxFS supports the following specific features for commercial applications:
— Pre-allocates space for files
— Specifies fixed extent size for files
— Bypasses the system buffer cache for file I/O
— Specifies the expected access pattern for a file
• Extended Mount Options
The extended mount options supported by VxFS include the following:
— Enhanced data integrity modes
— Enhanced performance modes
— Temporary file system modes
— Improved synchronous writes
— Large file sizes
20 Introduction