Volume scan

There has been some changes to the fsck when the unit boots up. When you do a reboot, the unit would run a fsck. Previously upon the boot up fsck it would write the changes. Currently upon a normal reboot and starts to run the fsck, it runs the fsck as a read-only. The message shows gives you a heads up to backup the data if the filesystem is too corrupted for the fsck to recover. These seem to be in extreme cases, but it is best to be caution than sorry that the data is missing.

It does appear that the filesystem check has been helping your unit for sometime, and running the offline fsck will write the changes. There is a chance the filesystem can get too corrupted for fsck, so it is recommended for the backups before running the offline filesystem checks with these messages.