Which is silly, and fails to isolate problems when/where they happen. Pretty much every significant level should have its own checksum, in many cases hopefully

Which is silly, and fails to isolate problems when/where they happen. Pretty much every significant level should have its own checksum, in many cases hopefully an ECC of some form. Hardware has bugs/failures as does software. What is particularly evil is when they both collide in a manner which causes silent/undetected corruption of important data for long periods of time.