As I am currently reduced to my backups of backups, I can give a pretty good figure. I am one of those people who never deletes anything. All backups are just made by copying the entire contents of my old PC onto a new one when the new one is first set up aside from a few special cases where I have external backups such as my cartoon and my music. My book is also backed up on floppy disks and optical medium.
At least 8TB (Yes, Terabytes) of data, some of which is duplicates but not a lot. Missing from these are a few drives, all of which were pretty much full;
> 1x 250GB drive with a broken connector. Was working before the connector broke off. Will be fixed and backed up when I have space.
> 1x 250GB drive from the same time period. Contains nothing important to me but I would like the data backing up when I have room.
> 1x 80GB ExcelStor, Contains the partition from one of my old Athlon XP systems. Has an incarnation of my cartoon on that wasn't around for long and currently has only a few images surviving on other drives.
> 1z 10GB ExcelStor which is broken, probably never get it working. Sucks, because it had the last remaining copy of an episode from my old cartoon series among other things.
> A bunch of old 2GB Seagate drives that aren't working. In use circa 2000-2001
> Whatever is left on my crappy IBM as there isn't a feasible way to get the data off it and it really isn't important past the fact it dates back to 1997. All the good stuff was on floppies I backed up anyway, so only crappy paint pictures and word documents I couldn't care less about are on there. In fact, the drive could have failed for all I know as I haven't started the machine in years.
> A 512MB memory stick from college. Was college property and I was meant to hand it in, but fuck them, I got keyboards and mice that belonged to them too... oops. Anyway, that stick has some scripts I made to compromise restrictions on the college computers. Interestingly, they are packaged into a word document. Some were never used, one allows modifying most aspects of the network connection's properties, thus allowing you to connect to different gateways and DNS which would bypass a lot of the restrictions if you knew what to connect to. There is also a "Patch" folder which fixes the holes I exploited in the system and I was going to hand this patch in on the last day. Unfortunately, IT Services were looking for the person who had caused major havoc with their system (I am saying nothing) and I thought it unwise to appear with a patch for the very security issues the prankster had just used. Also on that stick are a few prank programs I used to deploy regularly, one of them makes the screen look broken. They actually replaced several screens at college because of me bypassing Deep Freeze and making it start with the system, one tech even replaced the motherboard in the computer because he couldn't figure out what the problem was and assumed the video adapter had broken.
I am resigned to sort it out when I get a new machine, because there are nested directories on top of nested directories and it is becoming a headache. Large portions of what I have backed up are either music, my own music or my own videos. Very few photos. Bunch of word documents, mostly scripts I will never use, including a shitty film I scripted in one night when I was 15 years old and under the influence of both cannabis and alcohol. A massive collection of MIDI/WRK files. Bunch of SysEx for various synths. Stack of ISOs of software I backed up. Bunch of VHD and VFD images to make life easier when other machines break. All YouTube videos, some of which were never uploaded. One was shot in the home before the channel was set up and followed a spider's-eye view as it crawled along the ceiling and dropped onto my face with weird camera effects - was a bitch to film because I had no camera man and it turned out shit, hence I never uploaded it.
Oh, also, I just checked and my porn folder is at 114GB, 3520 files, 91 directories... Probably more as I have a directory missing from this backup... Yeah... Umm... I live on my own. Some of it dates back to the dial-up days and you can't really make out what you are seeing, it is just a pixellated flesh colored blur and the audio sounds like it is happening under water, might delete those as they aren't worth watching anymore really. Wonder how many hours of my life I have wasted that I will never get back.