Journal Checksumming in Ext3, Corruption and Recovery
In ext3 file system, journal is the most used and important file, since it is a journaled file system. But due to a drawback that ext3 doesn’t support checksumming while writing to the journal, file system becomes prone to corruption and hence may require Linux Data Recovery. In general terms, checksumming is the error detection technique if the file is corrupted or failing. But as ext3 doesn’t support the feature, recovering from corrupt journal can damage all metadata information of file system.
As such, system crash is recoverable if the file system supports journaling. But in ext3, if the mounting options in /etc/fstab doesn’t include barrier=1 as enabled plus hard drive is performing out-of-order write caching and system gets crashed, ext3 catches risk of corruption. Except in openSUSE, this barrier feature is disabled by default in all of the Linux distributions and so these systems can lose data due to system crash. Also, if user tries to use this mount option for ext3 that is going through device mapper interface, a warning is issued that barriers are not supported. Such systems can also cause file system corruption when a logical crash occurs.
In the conditions specified before the required blocks could be written, if user commits transaction and system crashes, it will reboot. During this, log replays and incomplete disk writing will be carried out with damaged journal information. This results into overwriting of normal data with that of damaged and hence file system corrupts. Data under these conditions can be recovered using Linux Recovery applications. Successor of ext3 that is ext4 supports journal checksumming.
About Linux Data Recovery
The Linux Recovery software can easily recover lost data from corrupt Linux volumes. These applications use safe scanning algorithms to extract lost data. In addition to that, they offer user friendly interface together with advanced recovery options that help users to perform an easy and largely automated recovery. These software are designed with read-only nature to offer complete peace of mind through their non-destructive nature. Apart from file system corruption, these products can solve all Linux logical data loss problems.
Stellar Phoenix Linux Data Recovery is the most powerful tool to recover lost data from Ext2, Ext3 and ReiserFS file systems based hard drives. The software can recover data from most of the Linux distributions like Red Hat, SUSE, Slackware, Turbolinux, Gentoo, Debian and others. The application can recover data in all logical data loss cases.
Allen Sood a student of Mass Communication doing research on data recovery> linux recovery and ext2 recovery software. He is also a freelancer for http://www.stellarinfo.com
Article Source: ArticlesBase.com - Journal Checksumming in Ext3, Corruption and Recovery