ext4 Backup Superblock Recovery: Verifying Data Integrity After Restoration

Goal

Determine whether data recovered from an ext4 filesystem using backup superblocks maintains integrity identical to the original files before corruption occurred.

Constraints and Uncertainty

ext4 stores multiple backup superblocks at fixed offsets (32768, 98304, 163840, 262144, etc.) that can restore filesystem structure when the primary superblock is damaged. However, the e2fsck utility requires manual specification of backup locations via the -b flag, and journal replay during mount may mask underlying corruption. The default 5% reserved blocks for root can also affect space calculations during restoration.

Key Questions

1. Can e2fsck with backup superblocks fully restore filesystem metadata without introducing inconsistencies that debugfs extraction cannot reveal?
2. How does ext4 journal replay behavior across kernel versions 4.x and 5.x+ affect the reliability of restored data compared to pre-corruption state?
3. What verification methods beyond checksum comparison can detect subtle data integrity issues that survive the backup superblock restoration process?