Newbie School: Brief Introduction to Linux File System Ext3 and ReiserFS

Although the kernel is the core of Linux, files are the main tool used for user interaction with the operating system. This is especially true for Linux, because in UNIX tradition, it uses file I/O mechanisms to manage hardware devices and data files.

The basic file storage units in Linux and UNIX are disk partitions, which are logical partitions of one or more hard disks. The operating system regards each logical partition as an independent disk. The file and file management system "lives" in the disk partition. Linux processes these disk partitions as devices and uses the file I/O mechanism through special files in the/dev directory.

Ext3: default file system of RedHat

Compared with Ext2, logs are added. Its main features are:

Availability): Ext3 provides the write consistency function for data. That is, in case of unexpected downtime, Data Consistency does not need to be checked, and the system recovery time is shortened from hours to seconds.

Data integrity): Use the mount command to define the log mode: data = journal. All Data, including file data and metadata, is defined as log type.

Speed): by defining the log mode: data = writeback, you can choose whether to obtain data integrity or write Speed advantages to meet different business needs.

Flexibility): It is very easy to upgrade from Ext2 to Ext3 without reformatting the hard disk. Run the command tune2fs and edit the file/etc/fstab to complete the upgrade. Note that Ext3 can be mounted as an ext2 file system without the log attribute.

In addition, many third-party manufacturers are compatible with Ext3 file systems, such as PartitionMagic.

ReiserFS: the default file system of SUSE LINUX

The default installed file system is the ResierFS developed by Hans Reiser. At the beginning of its design, it includes the following performance considerations From its initial design, key performanceaspects have included:

Log File System Journaling) is designed to improve reliability and recovery speed.

Using the data structure of the Balance Tree, you can store both content data and security metadata to achieve faster access.

Effective use of disk space. Unlike other file systems, ResierFS does not depend on the size of data blocks. Efficient use of disk space because, unlike other file systems, this file systemdoes not rely on block sizes.

Currently, the ReiserFS of suse linux Enterprise Server 8 is V3.6, and the next generation file system is Reiser4. Reiser4 provides an uninterrupted file system. By implementing the "atomic" file system, it avoids system crashes and ensures that I/O operations are completed; use the New Access Algorithm to obtain 2 to 5 times the performance improvement.

Tip: Red Hat Enterprise Linux AS does not support ReiserFS.

Select the log mode of the Ext3 File System

There are three log modes available for the Ext3 file system. The mount command is used to complete the process:

Data = journal

Both file data and metadata are set to log mode, with high performance overhead.

Data = ordered (default)

Write Data in sequence, Write File data first, and then write metadata

Data = writeback

Provides the fastest access speed, but sacrifices data consistency. The metadata is still recorded in the log to ensure the integrity of the metadata. The file data will be restored to the original state after the system crash.

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