tune2fs??
 

what does it do?

The manpage dno't help much:
tune2fs - adjust tunable filesystem parameters on second extended filesystems

is it mendotary to run it?

tunefs is used to switch filesystem from ext2 to ext3 and vice versa

tune2fs -j /dev/hda1 will switch ext2 to ext3

tune2fs -O has_journal /dev/hda1 will revert back to ext2 file system

also, when you revert ext2 to ext3, there r bits set in the file system that tells linux when to do a forced fsck on the disks. since ext3 doesnt need this, you can run tunefs -i 0 -c 0 /dev/hda1 to turn off forced checks.

HTH