> Journaling means every block has a checksum. No it doesn’t. Many journal filesystems use a checksum for log entries, but that is certainly not covering ever

> Journaling means every block has a checksum. No it doesn’t. Many journal filesystems use a checksum for log entries, but that is certainly not covering every block of the filesystem with a checksum. And that checksum only comes into play during log recoveries. Once a block is committed to disk there is no checksum in play (unless the fs has special support for it). Some newer journaling filesystems support metadata checksumming, but that is not some requirement to be journaling. XFS has not always supported metadata checksumming, and it’s a relatively recent addition to ext4 (like last decade). NTFS doesn’t do checksums on even metadata. This is one reason why ReFS is a thing.