Ext4 or Fourth Extended file system is an advanced and reliable Linux file system, which is successor of Ext3 file system. It is a journaling file system, which has emerged very quickly. It adds numerous performance improvements and remove the 64-bit data storage limitations. However, in case of system crash, you may lose your valuable data from Ext4 file system volume, due to delayed allocation. Data loss is a critical situation, which may put you in needs of Linux Data Recovery.
- Delayed Allocation is a feature of Ext4 file system, in which the blocks need to be allocated for holding the pending writes. The disk space for appended information is subtracted from free-space counter, however not really allocated in free-space bitmap. Alternatively, appended data remains in memory until it becomes necessary to be flushed to the storage media because of memory pressure or any other reason.
In Ext4 file system, Delayed Allocation causes some extra risks of the data loss if your system gets crashed before all the data is written to hard drive.
A common situations, in which it may occur, is an application replacing contents of file without forcing the write to hard drive with ‘fsync’. The problems may occur if your system crashes before actual write operation completes. The Ext4 file system code generally clears the file contents before system crash and do not write new version. Ext4 file system uses 2.6.28 version of Linux kernel.
Modifying the behavior of Ext4 file system through ‘fsync’ can cause severe performance issues on hard drive volumes, which are mounted with data=ordered flag using Ext3 file system.
Along with the Delayed Allocation issue, there are some implementation bugs of Ext4 file system that can cause severe file system metadata corruption. In such cases, operating system cannot find the essential data structures on hard drive and thus you cannot access data stored on the Linux hard drive volumes.
Work Around
You can prevent this problem by using the 2.6.30 version of Linux kernel, which has patches to solve this problem. In such situations,
Linux Recovery is the only way to get your data back.
To recover the lost data, you need to scan your hard drive using third-party
Ext4 Recovery software. They perform Data Recovery Linux in all cases of logical failure and data loss. The applications are safe and easy to use.
Stellar Phoenix Linux Data Recovery is a powerful utility that ensures absolute recovery of your lost, missing, and inaccessible data from Linux hard drive. It retrieves data from Ext4, Ext3, Ext2, FAT32, FAT16, and FAT12 file system volumes. The software is usable with all major distributions of Linux operating system, such as Red Hat, Debian, Mandriva, SUSE, and Ubuntu.
