HP JFS 3.3 and HP OnLineJFS 3.3 VERITAS File System 3.3 System Administrator's Guide

96 Chapter5
Performance and Tuning
Choosing Mount Options
tmplog
In tmplog mode, intent logging is almost always delayed. This greatly
improves performance, but recent changes may disappear if the system
crashes. This mode is only recommended for temporary file systems. Fast
file system recovery works with this mode.
nolog
Same as tmplog.
nodatainlog
The nodatainlog mode should be used on systems with disks that do not
support bad block revectoring. Normally, a VxFS file system uses the
intent log for synchronous writes. The inode update and the data are
both logged in the transaction, so a synchronous write only requires one
disk write instead of two. When the synchronous write returns to the
application, the file system has told the application that the data is
already written. If a disk error causes the data update to fail, then the
file must be marked bad and the entire file is lost.
If a disk supports bad block revectoring, then a failure on the data
update is unlikely, so logging synchronous writes should be allowed. If
the disk does not support bad block revectoring, then a failure is more
likely, so the nodatainlog mode should be used.
A nodatainlog mode file system should be approximately 50 percent
slower than a standard mode VxFS file system for synchronous writes.
Other operations are not affected.
blkclear
The blkclear mode is used in increased data security environments.
The blkclear mode guarantees that uninitialized storage never appears
in files. The increased integrity is provided by clearing extents on disk
when they are allocated within a file. Extending writes are not affected
by this mode. A blkclear mode file system should be approximately 10
percent slower than a standard mode VxFS file system, depending on the
workload.