I need to downgrade a system from Centos x4.2 to v3.6 (x86) due to performance problems with Arkeia Network Backup and AIT-4 tape drives. The backup database is stored on a v4.2 created ext3 partition. When accessing this partition after the downgrade, Centos complains on boot that fsck.ext3: Filesystem has unsupported feature(s) (/dev/sda5) *fsck: Get a newer version of e2fsck! [fail] If I comment the partition out of /etc/fstab the machine boots as normal and I can manually mount the filesystem. My questions are: If I use the v4.2 ext3 filesystem on v3.6 I am likely to corrupt the data? And what is the best way fix this problem? Do as it says and try and upgrade e2fsck or is there a better fix? Thanks Dean.