File systems: Journaling and Error Correction (general)
Posted on 2016-08-08
I am making my first array into the world of Linux and I have two questions which I believe is also inherent to a number of other operating systems. In my Linux book there is a short passage about fault-resilience and error correction and as the passage was very short, I looked did some online research which confused me even more.
My fist question is about the journaling
I understand that there are two methods of journaling: logical and physical and only the latter provides for full system recovery.
How can a logical/meta-data only journaling support system recovery? Is it like the system logs in Windows which informs the user which device or software has caused an error? Then it's up to the user to decide how to proceed?
On Wikipedia I read that "After a crash, recovery involves reading the journal from the file system and replaying changes from this journal until the file system is consistent again. " I assume this applies to the physical logging only?
My last question is about error checking:
Every time a user saves a file, a check value is stored alongside (or inside?) the file. Is this called the check value also known as the check sum? The same process is done when the file is opened. If the values don't match, then there was an error. Is this done with a function known as Cyclic Redundancy Check? Or am I mixing things up?
Thank you for your help.