Veritas™ File System 5.0.1 Administrator's Guide

■ Multi-volume support

The multi-volume support feature allows several volumes to be represented

by a single logical object.

■ Dynamic Storage Tiering

The Dynamic Storage Tiering (DST) option allows you to configure policies

that automatically relocate files from one volume to another, or relocate files

by running file relocation commands, which can improve performance for

applications that access specific types of files.

■ Storage Foundation Thin Reclamation

The Thin Reclamation feature allows you to release free data blocks of a VxFS

file system to the free storage pool of a Thin Storage LUN. This feature is only

supported on file systems mounted on a VxVM volume.

Note: VxFS supports all HFS file system features and facilities except for the

linking, removing, or renaming of “.” and “..” directory entries. Such operations

may disrupt file system sanity.

Extent-based allocation

Disk space is allocated in 1024-byte sectors to form logical blocks. VxFS supports

logical block sizes of 1024, 2048, 4096, and 8192 bytes. The default block size is

the larger of 1K or the device's hardware sector size for file system sizes of up to

1 TB, and 8K for file system sizes 1 TB or larger.

An extent is defined as one or more adjacent blocks of data within the file system.

An extent is presented as an address-length pair, which identifies the starting

block address and the length of the extent (in file system or logical blocks). VxFS

allocates storage in groups of extents rather than a block at a time.

Extents allow disk I/O to take place in units of multiple blocks if storage is allocated

in consecutive blocks. For sequential I/O, multiple block operations are

considerably faster than block-at-a-time operations; almost all disk drives accept

I/O operations of multiple blocks.

Extent allocation only slightly alters the interpretation of addressed blocks from

the inode structure compared to block based inodes. A VxFS inode references 10

direct extents, each of which are pairs of starting block addresses and lengths in

blocks.

The VxFS inode supports different types of extents, namely ext4 and typed. Inodes

with ext4 extents also point to two indirect address extents, which contain the

addresses of first and second extents:

Introducing Veritas File System

Veritas File System features