On Windows, we’ve had the defrag tool and others, that happily works on a drive even while it is in use, even the OS disk.
On Linux, I know of the fsck command but that requires the drive in question to be unmounted. Not great when you want to check a running server. I do not want to stop my server and boot it from USB, just to run a disk check. I can’t imagine that’s what the data centers are doing, either!
Surely some Linux tool exists that can do some basic checks on a running system?
They don’t do anything.
They have lots and lots of redundancy, and when enough drive fails, they decommission the entire server and/or rack.
Them big players play at a very different scale than the rest of us.