Soft Updates Help

[Sean Murphy]

I have read up on soft updates and have some questions.

The way that I am understanding soft updates purpose is to allow file 
systems to be mounted dirty after an unclean shutdown of the system.  
This will allow fsck to run in the background to restore the consistency 
of the file system which is compared against a snapshot of the system.  
It also increases performance of heavily written file systems by waiting 
to write the metadata of files and directories until a more opportune time.

I have questions about this.

When is the snapshot taken, how often, do I have to do it or does a 
program or kernel do it?

If this is a safe way to restore consistency why is it not used on /?

If a file system is not heavily written to is it better not to use soft 
updates?

How do I know when the background fsck is finished and if it was successful?

Do I have to add anything to enable the backgound fsck?

When file systems are mounted dirty and our being used while the 
backgound fsck is running on the file systems how does it prevent files 
from being lost?




Thanks