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VERITAS File System 3.5 (HP OnlineJFS/JFS 3.5) Administrator's Guide: HP-UX 11i v2 > Chapter 1 The VERITAS File System
Extended mount Options |
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The VxFS file system supports extended mount options to specify:
See Chapter 2 “VxFS Performance: Creating, Mounting, and Tuning File Systems” and the mount_vxfs(1M) manual page for details on the VxFS mount options.
Most file systems are “buffered” in that resources are allocated to files and data is written asynchronously to files. In general, the buffering schemes provide better performance without compromising data integrity. If a system failure occurs during space allocation for a file, uninitialized data or data from another file may appear in the extended file after reboot. Data written shortly before the system failure may also be lost. In environments where performance is more important than absolute data integrity, the preceding situation is not of great concern. However, VxFS supports environments that emphasize data integrity by providing the mount -o blkclear option that ensures uninitialized data does not appear in a file. VxFS provides the mount -o mincache=closesync option, which is useful in desktop environments with users who are likely to shut off the power on machines without halting them first. In closesync mode, only files that are written during the system crash or shutdown can lose data. Any changes to a file are flushed to disk when the file is closed. File systems are typically asynchronous in that structural changes to the file system are not immediately written to disk, which provides better performance. However, recent changes made to a system can be lost if a system failure occurs. Specifically, attribute changes to files and recently created files may disappear. The mount -o log intent logging option guarantees that all structural changes to the file system are logged to disk before the system call returns to the application. If a system failure occurs, fsck replays any recent changes to preserve all metadata. Recent file data may be lost unless a request was made to sync it to disk. VxFS has several mount options that improve performance such as delaylog and qlog. The default VxFS logging mode, mount -o delaylog, increases performance by delaying the logging of some structural changes, but does not provide the equivalent data integrity as the previously described modes. That is because recent changes may be lost during a system failure. This option provides at least the same level of data accuracy that traditional UNIX file systems provide for system failures, along with fast file system recovery. delaylog is the default mount option. On most UNIX systems, temporary file system directories (such as /tmp and /usr/tmp) often hold files that do not need to be retained when the system reboots. The underlying file system does not need to maintain a high degree of structural integrity for these temporary directories. VxFS provides superior performance for synchronous write applications. The default mount datainlog option greatly improves the performance of small synchronous writes. The mount convosync=dsync option improves the performance of applications that require synchronous data writes but not synchronous inode time updates.
VxFS can support files up to two terabytes in size. See “largefiles | nolargefiles” for information on how to create, mount, and manage file systems containing large files.
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