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Online system administration

VxFS provides a comprehensive list of command line interface (CLI) operations that are described throughout this document and in manual pages.

A VxFS file system can also be defragmented and resized while it remains online and accessible to users. The following sections provide an overview of these features.

About defragmentation

Free resources are initially aligned and allocated to files in an order that provides optimal performance. On an active file system, the original order of free resources is lost over time as files are created, removed, and resized. The file system is spread farther along the disk, leaving unused gaps or fragments between areas that are in use. This process is known as fragmentation and leads to degraded performance because the file system has fewer options when assigning a free extent to a file (a group of contiguous data blocks).

VxFS provides the online administration utility fsadm to resolve the problem of fragmentation.

The fsadm utility defragments a mounted file system by performing the following actions:

This utility can run on demand and should be scheduled regularly as a cron job.

About file system resizing

A file system is assigned a specific size as soon as it is created; the file system may become too small or too large as changes in file system usage take place over time.

VxFS is capable of changing the file system size up or down while in use. Many competing file systems can not do this. The VxFS utility fsadm can expand or shrink a file system without unmounting the file system or interrupting user productivity. However, to expand a file system, the underlying device on which it is mounted must be expandable.

VxVM facilitates expansion using virtual disks that can be increased in size while in use. The VxFS and VxVM packages complement each other to provide online expansion capability. Use the vxresize command when resizing both the volume and the file system. The vxresize command guarantees that the file system will shrink or grow along with the volume. Do not use the vxassist and fsadm_vxfs commands for this purpose.

See the vxresize(1M) manual page.

See the Veritas Volume Manager Administrator's Guide.