I am trying to understand the difference between File system consistent and crash consistent backups provided by Azure.
The majority of the information that I find is from this link.
I see Application consistent backup is to ensure that all memory data and pending I/O are accounted for perhaps by using a quiescing process so proper snapshot can be taken. However bit confused between the other two. I see Crash consistent is one which doesn't consider the in-memory, pending I/Os and only considers backing up what has been written. But then what exactly would be meant by file-consistent backup? I don't find any definition. As a result when the docs mention that by default Linux VM backups are File system consistent if not using pre/post scripts, I am not understanding the implications. Any help much appreciated.
Simple example to demark the difference is : when a recovery point is file-system consistent, there won't be any file system check performed to make sure that file system is not corrupted. In case of crash consistency, after a VM boots up, a file-system check may be performed and based on that there can be potentially a data loss because of corruption of file system. So, it is always better to strive for file system consistency.