Tham khảo tài liệu 'wiley publishing suse linux 9 bible phần 3', ngoại ngữ, ngữ pháp tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 78 Part I SUSE Linux Basics What Is a Journaling Filesystem A journal with respect to filesystems is an area of the disk that is used to store information about pending changes to that filesystem. Filesystems contain two general types of information the actual files and directories where your data is stored and filesystem metadata which is internal information about the filesystem itself where the data for each file is physically stored which directories contain which files and so on . When you write to a file in a journaling filesystem the changes that you want to make are written to the journal rather than directly to the file. The filesystem then asynchronously applies those changes to the specified file and updates the filesystem metadata only when the modified file data has been successfully written to the file in question. Journaling helps guarantee that a filesystem is always in a consistent state. When you reboot a Linux system Linux checks the consistency of each filesystem using a program called fsck for file system consistency check before mounting it. If a filesystem requires repair because its consistency cannot be verified the fsck process can take a long time especially on larger disks. Enterprise systems tend to require journaling filesystems to minimize the time it takes to restart the system because downtime is generally frowned upon. There are certain situations where the use of a journaling filesystem can be a bad idea most notably with databases that store their data in a standard Linux filesystem but that keep their own log of changes to those data files and are able to recover data using their own internal methods. Oracle is a good example of a database that provides its own methods to guarantee the consistency of its data files. EXT2 EXT2 has been the de facto Linux filesystem for many years and is still used for initial ramdisks and most non-journaling filesystems. Because of its age EXT2 is considered extremely stable and is quite .
