78s and 45s are still better than digital.
Old 78s and 45s were never better than digital, in any fashion. They added weight and ceremony to listening to music, because of the care needed in using them. They added distortions that people like to call "warmth". Both of these are form, and run in direct violation to their primary function as a storage medium.
I'm somewhat confused. Each ATSC channel is a fixed 6 MHz wide spectrum. They can either do one HD channel or four SD channels
There's no explicit maximum, or at least none that you could ever reasonably reach. It all comes down to how much you compress the data. You can run dozens of HD channels on a single multiplex if they look like shit, or are primarily static images.
At the end of the day, all I know is that stations which once were viewable (some even perfect) under analog are no longer viewable under digital.
That sounds like other changes were made at the same time, independent of the digital transition. Their new transmitters are cheap shit. They dropped to a lower transmit power. They moved to a different antenna or frequency that results in increased interference.
Are you sure about that? ZFS has a "copies" parameter as well. It just means it stores two copies of the block somewhere in the pool. If you give it multiple disks in a pool, it will try to place those copies on different disks, but it will not guarantee it. It's a measure to prevent data loss when you have a damaged sector, not a full disk failure.
If you have disks of different sizes with copies=2, will it refuse to write if you only have one disk with free space remaining?
With btrfs RAID1, which is what I'm using, you throw a drive in, hit rebalance, and you now have more storage, properly mirrored with distributed metadata.
If you have RAID1 and add a drive, you still have RAID1, and just as much storage as you started with. You only add redundancy, unless you're saying it converted the mirror into a parity array.
The same can be said for any other filesystem as well. If you have a bad bit in memory, and you write it to disk, that data is corrupted. The only penalty under ZFS is that if you gave it redundancy, and leave checksums enabled, it will detect that fault, try to correct it, and in doing so crush the whole block instead of just one bit.
If you aren't going to use ECC memory, don't use checksums either.
So you can't expand an existing vdev
While you cannot add new drives to a vdev, you can expand a vdev by incrementally replacing all of its drives with larger versions. Replace a drive, resilver, replace a drive, resilver... and when you're all done, just export the pool, import it back, and you have the full capacity of the new drives available.
1 + 1 = 3, for large values of 1.