which errors are critical for integrity of ext[234] file system?

[Martin T <m4rtntns@gmail.com>]

I was playing with dd "conv=noerror" option. It continues reading the
input file(for example HDD/SSD partition) even in case there are read
errors. Which errors are critical for integrity of ext[234] file
system? As I understand, Linux views the file system as a common set
of objects- superblock(maintains and describes the state of the file
system), inode(unique identifier for all the file system objects and
contains necessary metadata), dentry(glues together inode number and
file name), and file(bunch of bytes arranged in a certain order). Am I
correct that if the main superblock is damaged, the spare one is used
by fsck? In addition, am I correct that if sectors which hold content
of a file(for example .avi movie) are damaged, then only this file is
corrupted but file system itself is in good shape?


regards,
martin