Managing Systems and Workgroups: A Guide for HP-UX System Administrators

Planning a Workgroup
Planning to Manage File Systems
Chapter 2 95
delaylog Delayed logging. Some system calls return before the
intent log is written. This enhances the performance of
the system, but some changes are not guaranteed until
a short time later when the intent log is written. This
mode approximates traditional UNIX guarantees for
correctness in case of system failure.
tmplog Temporary logging. The intent log is almost always
delayed. This improves performance, but recent
changes may disappear if the system crashes. This
mode is only recommended for temporary file systems.
nolog No logging. The intent log is disabled. The other three
logging modes provide for fast file-system recovery;
nolog does not provide fast file system recovery. With
nolog mode, a full structural check must be performed
after a crash; this may result in loss of substantial
portions of the file system, depending upon activity at
the time of the crash. Usually, a nolog file system
should be rebuilt with mkfs after a crash. The nolog
mode should only be used for memory resident or very
temporary file systems. (See mkfs_vxfs (1M).)
What write options are available using JFS?
JFS provides several options to control how user data is written to disk:
sync Synchronous writes. Writes block until the data
specified in the write request and all file attributes
required to retrieve the data are written to the disk.
dsync Data synchronous writes. A write operation returns to
the caller after the data has been transferred to
external media. However, if only the times in the inode
need to be updated, the inode is not updated
synchronously.
closesync sync-on-close writes. sync-on-close I/O mode causes
writes to be delayed rather than to take effect
immediately, and causes the equivalent of an fsync (2)
to be run when a file is closed.
delay Delayed writes. This causes writes to be delayed rather
than to take effect immediately. No special action is
performed when closing a file.