ext3 doubts, why it checks for file system during boot ?

[mohit.saha]

If journaling can be used to recover file system after crashes, why does ext3 still ask for file system check during system boot up?

[Ricky]

Well, it is not hard question,  you can get answer yourself .
May be I can explain. ..
We know that journalized file system makes it easy to keep data reliable and even faster as compared to non-journalized file system. For that it maintains a Journal.. ie. record some system level file reading / writing  operation log... so when there is  a crash.. it just checks log and make sure that no operation is left incomplete.. hence maintaining data consistency.
So basically.. it also need to verify Journal etc.. and that is relatively very quick. `

[dragoncity99]

To what i understand is:

Journalling helps u to recover corrupted data back to the previously synced to disk data from the buffer.

Any unclean reboot/reboot can cause this based on the runlevel scripts deployed by the Linux distro to make sure no data corruption. If we dont do that, there is a risk to the data integrity.

Also, it will always force a check, when ur ext3 is customized in such a way where after a period of time, u must do a force filesystem check.

Use tune2fs utility to check the ext3 filesystem for it's tuning info.