Yours was the best of the bunch (minus formatting html tags), though I enjoyed reading about the trials and tribulations of punch tape vs punch cards vs tape/dat backup systems. The biggest problem I had many years ago was using a dat format system that I could not longer purchase hardware for. So I had tapes, but no way to read them. That taught me a lesson. Never use a media that I might not be able to read from 10 years from today. Thus I only backup on hard disks today.
I agree that to backup music, videos and other static content that has been downloaded via the internet (and not personally created) is a waste of time and space. As you pointed out, with even a throttled cable connection you can download this fairly quickly. So never waste time backing it up. Totally agree with you.
Now the one exception to video, pictures and music, are those that you create yourself. For your own personal pictures and personally created video. That needs to be backed up and I would suggest a harddrive (or multiple hard disks) for this purpose.
If you work in the video / movie industry creating content, obviously this comment does not apply to you...check into creating your own Linux video sever farm for while-you-sleep-rendering and a homemade Linux SANs like this Petabytes on a budget: How to build cheap cloud storage. You will have to learn some Linux to do this, but it would be well worth it, if you have the need. This article should help you, Thoughts about this DIY-Thumper and storage in general
Just as with industrial and union jobs of yesterday, white collar IT jobs, your movie editing jobs are now being offshored to India and when I was in LA a couple of years ago, a number of studios were relocating to Canada because it was cheaper for them...fyi.
For home users not in an industry creating massive videos, the next few paragraphs should cover you. Give thoughts to what you really need and why. Don't back up anything you do not have too. Like Software, Operating Systems, only focus on the data you create.
Plan your locations for different types of data, since you can label (mount point) your directory whatever you want. You could have one for video, one for audio (music), one for non picture images (your digital camera) and one for everything else. If you have the need, perhaps a DB directory as well. This would look as follows:
/video/ ~ for downloaded video, not home movies, never backed up (this will be your largest directory for most)
/music/ ~ for downloaded music, not self created, never backed up (you could write this to DVR or copy to a USB thumb drive if you want, the files are NOT that big. A 64GB thumb drive costs less than $30 on sale. Get a Micro USB adapter and only purchase micro SD cards and get very large ones. I use to use 8GB in my Nokia N800, now my zareason ZT2 Tablet has a 32GB micro SD card in it. Since I am using it for books, PHP development and research only, it will take a very long time to fill up.)
/myvideo/ ~ personally made video, back it up
/mymusic/ ~ personally created music, back it up
/images/ ~ digital images from your digital camera, back it up
/db/ ~ custom database stuff, back it up
/data/ ~ everything else, back it up
For the majority of you reading this, from /myvideo/ to /data/ (five different directories) will easily fit on one 500GB drive. If you are smart and compress it when you backup, you can probably fit a months worth of backups on that 500GB drive if not more. Linux comes with built in compression / backup commands and you can use PKZIP (or other compression program) for Windows to compress your data sizes and make your backup space go further. Even more if your backup method / scripts are smart enough to do a full once per week and than incrementals after that. Though today, its probably just as easy to do fulls each time and not full with incremental backups.
If you do not trust yourself to keep your data below your arbitrary minimum, whether 500GB, 1TB or 2 TB, that too is easly fixed, just create spaces (mounts points / partition sizes) below your arbitrary minimums and don't worry about it until you hit your limit. Granted its much easier to grow spaces in Linux than Windows, but that is another side issue.
As long as you do not let any of the above drives / directories grow larger than your backup hard drive, you will not have a problem creating the backups and if necessary restoring files from those backups. The number of hard drives you need would only depend upon your rotation / backup needs. Thus after a month, you could potentially re-use a hard drive.
Only the data you need from day to day, week to week, month to month, needs to be backed up. And unless you are doing something with really BIG data this backup will NOT approach 20TB in the near future. Perhaps 1TB if you save allot of stuff, though that would surprise me...you would have to be in the 1% of home users to hit 1TB. Most home users will be hard pressed to fill up a 500GB drive with data only, no videos, no music. If compressed, most home users would not fill up a 500GB drive with a month of backups.
The key to the plan is to limit the size of your data in any one location to less than the size of your backup device (500GB, 1TB, 2TB). If you use 500GB hard disks to back up your data (hot swappable) than each of those data drives should be limited to less than 500GB.
Get a HDDRACK5 from Sans Digital ($29.99 per). Its a 5 bay rack that can be used with SATA drives straight off your computer. Simply keep at least one bay for backups and make sure to limit the size of your data on all your other disks to less than the size of your backup drive, 500GB, 1TB or 2TB should do nicely. And you are good to go. Some hardware configuration is required. If you do not want to do this, there are $200 - $500 plus options for you, search.
Still you do not waste backup space backing up any content that you do NOT create yourself.
And since net neutrality is in jeapordy due to the recent court cases, should the cable providers institute broadband caps as they have always wanted to do, even tried a few times, but supposedly say they won't...yea right, not buying it. You will not be forced to pay extra charges because your backup is in your home with you.
The through the internet backup tools are great today, I just have zero faith that the cable providers will not add in a cap one day, especially now that Time Warner and Comcast are going to merge. If caps hit and you are backing up over the internet, good luck.
For offsite backups you could rotate a drive out of your house to your safety deposit box or the home of a family member, just in case. Those fireproof lock cases are cheap at the local business store and will hold more than one SATA drive.
As others have pointed out, as your data grows in size, the time it takes to restore from backup grows as well. Ultimately as are local data grows, the time it takes to backup and restore will become the major impediment to the viability of your backup system.
Most importantly, whatever backup system you decide upon, practice restoring your data a couple of times per year. Better that, thant to find out after the fact your data did not get backed up correctly. You honestly do not know if you have not tried to restore, if your backup system works or not. This is more common than you realize. Test your restore before relying on it.
Thus a full restore, worst case scenario is:
Restore operating system (can you do this for your handheld or tablet? if not your backups may be useless.)
Restore software from source
Create directory structure you use
Hope this helps many of you.
For all those that contributed the information and humor about punch tape, magnetic tape, punch cards, dat, etc.. you all made my day. Thanks for the trip down memory lane. The only media I did not use was punch tape. Also I never punced core, though one of my professors in college did. Should have asked him how he backed up that punched core. LMAO. Wonder if it beat the tape cassettes that came with the Radio Shack Model I...probably not.
Remember how fast the floppy disk drive in the Radio Shack Model III seemed...also too funny.
The tape system that I could not easily get was a Sytos tape backup system, worked great with OS/2 1.3 EE and OS/2 Warp, until the Sytos hardware died on me. At that point I was not going to waste more money on that backup system.