UFS Logging Is Enabled by Default (System Administration Guide: Devices and File Systems)

System Administration Guide: Devices and File Systems

UFS Logging Is Enabled by Default

Solaris 9 9/04 – Logging is enabled by default for all UFS file systems except under the following conditions:

When logging is explicitly disabled.
If there is insufficient file system space for the log.

In previous Solaris releases, you had to manually enable UFS logging. For more information about UFS logging, see UFS Logging.

Keep the following issues in mind when using UFS logging in this release:

Ensure that you have enough disk space for your general system needs, such as for users and applications, and for UFS logging.

If you don't have enough disk space for logging data, a message similar to the following is displayed:

# mount /dev/dsk/c0t4d0s0 /mnt
/mnt: No space left on device
Could not enable logging for /mnt on /dev/dsk/c0t4d0s0.
#

However, the file system is still mounted. For example:

# df -h /mnt
Filesystem             size   used  avail capacity  Mounted on
/dev/dsk/c0t4d0s0      142M   142M     0K   100%    /mnt
#

A UFS file system with logging enabled that is generally empty will have some disk space consumed for the log.
If you upgrade to this Solaris release from a previous Solaris release, your UFS file systems will have logging enabled, even if the logging option was not specified in the /etc/vfstab file. To disable logging, add the nologging option to the UFS file system entries in the /etc/vfstab file.

Default Logging and Standards Conformance

UFS file system transactions that free blocks from files might not immediately add the freed blocks to the file system's free list. This behavior occurs on a system that has a UFS file system mounted with logging enabled.

This behavior improves file system performance, but does not conform to the following standards:

POSIX, Single UNIX® Specification
SPARC® Conformance Definition
SPARC Conformance Definition System V Application Binary Interface
System V Interface Definition
X/Open® Portability Guide

These standards require that freed space be available immediately.

Consider disabling UFS logging under the following conditions:

You want to enable standards conformance regarding file deletions.
You encounter problems creating or growing files immediately after the files have been deleted on a relatively full file system.

For more information, see mount_ufs(1M).