Exploring the ext3 Filesystem
来源:互联网 发布:2017网络作文大赛参加 编辑:程序博客网 时间:2024/05/18 09:50
journal - logs all filesystem data and metadata changes. The slowest of the three ext3 journaling modes, this journaling mode minimizes the chance of losing the changes you have made to any file in an ext3 filesystem.
ordered - only logs changes to filesystem metadata, but flushes file data updates to disk before making changes to associated filesystem metadata. This is the default ext3 journaling mode.
writeback - only logs changes to filesystem metadata but relies on the standard filesystem write process to write file data changes to disk. This is the fastest ext3 journaling mode.
The differences between these journaling modes are both subtle and profound. Using the "journal" mode requires that an ext3 filesystem write every change to a filesystem twice - once to the journal, and then again to the filesystem itself. This can reduce the overall performance of your filesystem, but is the mode most beloved by users, because it minimizes the chances of losing changes to your files since both metatdata and data updates are recorded in the ext3 journal and can be replayed when a system reboots.
Using the "ordered" mode, only filesystem metadata changes are logged, which reduces redundancy between writing to the filesystem and to the journal and is therefore faster. Though the changes to file data are not logged, they must be done before associated filesystem metadata changes are made by the ext3 journaling daemon, which can slightly reduce the performance of your system. However, using this journaling mode guarantees that files in the filesystem will never be out of sync with any related changes to filesystem metadata.
Using the "writeback" mode is faster than the other two ext3 journaling modes because it only logs changes to filesystem metadata and does not wait for associated changes to file data to be written before updating things like file size and directory information. Because updates to file data are done asynchronously to journaled changes to filesystem metadata, files in the filesystem may exhibit metadata inconsistencies such as owning data blocks to which updated data was not yet written when the system went down. This isn't fatal, but can be disappointing to users.
Specifying the journaling mode used by an ext3 filesystem is done in the /etc/fstab entry for that filesystem. The "ordered" journaling mode is the default journaling mode by ext3 filesystems, but you can specify a different journaling mode by updating the filesystem options portion of an /etc/fstab entry. For example, an /etc/fstab entry that specifies the "writeback" journaling mode would look like the following:
/dev/hda5 /opt ext3 data=writeback 1 0
- Exploring the ext3 Filesystem
- ext3 filesystem bad superblock recovery
- Hybris-Exploring the Installation
- Resolving Ext3 Error: No journal on filesystem
- Exploring the Internet Explorer WebControls...
- Exploring the /proc/net/ Directory
- Exploring the world of Android
- The mini_fo filesystem
- The Hadoop Distributed Filesystem
- Extend ext3 filesystem for RH5 Virtual Machine running in vCluster
- Exploring the C++ Unit Testing Framework Jungle
- Exploring the C++ Unit Testing Framework Jungle
- Exploring C++: The Programmers Introduction to C++
- Exploring the 'Dao' of Search---Sun Liang
- EXPLORING THE WORLD OF ANDROID :: PART 2
- Exploring the C++ Unit Testing Framework Jungle
- Exploring the world of Android :: Part 2
- Exploring the world of Android :: Part 2
- MYSQL不能从远程连接的一个解决方法
- MySQL安装笔记
- MYSQL 的 MASTER到MASTER的主主循环同步
- Mysql 常用命令 转
- MYSQL完整安装和主从双机配置
- Exploring the ext3 Filesystem
- 自己动手提高ubuntu系统的性能(EXT3)
- 虚拟机学习系列 - 5 - 内存分配与回收策略
- 全面了解安装使用Linux下的日志文件系统
- 传统网络配置命令与IP高级路由命令
- TCP segmentation offload
- 怎样取得文件行数
- WebTrends Log Analyzer
- Tcpdump命令的使用与示例——linux下的网络分析