Want a real archival backup that your great-great-grandchildren will be able to read?

Most media (CD-Rs, tape, disk, I think also flash) decay after 10 to 20 years. Having lots of redundant copies helps a little, but only a little.

If you want things to last a LONG time (say, 100+ years), I think the best options today are:

1 – M-DISC BluRay discs. They are designed to last 100 years. Of course this hasn’t been tested – the number is based on projections and knowledge of the decay mechanisms. From what I’ve read the chance of them being readable after 200 or 300 years is pretty good, if they’re stored in a dark cool place (say 5 to 10 C). Probably purging the oxygen from the container (flush it out with nitrogen) is a good idea too.

And, of course, multiple redundant copies.

2 – Multiple external HDDs, but keep them running the whole time (bearings often seize up after a few years if they’re not run). Actively migrate the data to new hardware every 10 years or so. (This requires money and effort of course.)

My understanding is that the ZFS (Zettabyte File System) is the way you’d want to store data across multiple HDDs – you can adjust the redundancy level as you like and ZFS will use all available space to create more redundancy if you want (as you originally where thinking).

3 – If you only have a little bit of data to store (< 1 MByte) – punched paper tape or punched cards. Store them in sealed containers purged of oxygen, in a dark cool place. If you’re really serious, use punched cards made of out of solid gold (gold is inert), and put the sealed container in a Nazi submarine and sink it to the bottom of an ocean.

Are you concerned that 100+ years from now nobody will have the hardware to read the media? Don’t be. If civilization doesn’t fall, it won’t be a problem (if it does fall, yes a problem).

I don’t think there’s any storage media used 100 years ago that we can’t today build a new reader for – easily and cheaply. And of course there will always be historians and museums who keep readers functional for common media.

Re uncommon media, a few years ago there was a project to recover data from some 50 year old tapes with data from NASA spacecraft. There were no working tape drives that could read it, so they built a new one from scratch. Anything we can build today at all, the technology of the future (assuming civilization doesn’t collapse) will find easy to duplicate.

[Minor update 2020-09-06, larger update 2025-10 for BC5]

I use Beyond Compare a lot – every day. It’s the best “diff” utility I’ve ever found.

But I also need to compare Word documents a lot – also every day. And Beyond Compare isn’t very good at that.

Microsoft Word has it’s own “legal blackline” for tracked changes (sometimes called “redline”) compare which works well, but is very tedious to start each time. To use it (in Office 365), you need to:

1. Open a document
2. Go Review>Compare>Compare two documents
3. Find the original document and select it
4. Find the revised document and select it (yes, even tho you already have it open)
5. Click OK

If, as is often the case with me, the two documents are in different folders, this is a lot of work.

With Beyond Compare, on the other hand, you can just select two documents in File Explorer, and right-click on “Compare”. Done.

Here’s a way to get Beyond Compare (BC) to launch Word’s legal blackline, the same easy way. Step-by-step:

1 – Put script “diffword.ps1” into the BC5 settings folder (usually “%appdata%\Scooter Software\Beyond Compare 5”)

(That file is based on an idea I found at https://github.com/ForNeVeR/ExtDiff – many thanks to the author of that!!)

2 – Open Beyond Compare and do Tools>FileFormats… Uncheck any pre-existing “MS Word Documents” setup under the Name column on the left.

3 – Go to the bottom of the window that pops up and click ‘+’, then choose “External Format”.

4 – In the Mask box paste in “*.doc;*.docm;*.docx;*.dot;*.dotm;*.dotx” (without the double quotes).

5 – In the Quick compare command line box paste in (again without the double quotes): “powershell -NoProfile -STA -ExecutionPolicy ByPass -File “%appdata%/Scooter Software/Beyond Compare 5/diffword.ps1″ %1 %2”

6 – In the Compare view command line box paste in exactly the same thing (again without the double quotes): “powershell -NoProfile -STA -ExecutionPolicy ByPass -File “%appdata%/Scooter Software/Beyond Compare 5/diffword.ps1″ %1 %2”.

7 – In the Description box paste in (if you care): “Make MS Word open it’s own legal blackline (aka redline) compare.”

8 – Click Save

9 – The new file format should be at the very top of the list on the right (in case of more than one setup in this list, Beyond Compare uses the first one in the list). Just to make it look clean, right-click on the name of your new format and change the name to “MS Word”.

The window should look like this:

To use it:

1 – Right click on the ORIGINAL file and choose “Select left file for compare”.
2 – Right click on the REVISED file and choose “Compare to”.

You can also just select two Word files with File Explorer (drag the mouse around them, ctrl+leftclick on each, or shift+click). Then right-click on the ORIGINAL document and say “Compare”. (Whichever document you right-click on Word considers the original.)

That’s it. This will open a Word window with the blackline change marks (revised marked against original).

Supposedly

del /f/s/q [target]

But often it doesn’t – excessively long file names, excessively long paths, and other things, break it. Sometimes it can be quite difficult to fully clean out a folder.

There are many solutions (cygwin‘s rm is pretty powerful) but here’s a simple batch file that harnesses the power of Robocopy (which comes pre-installed with Windows) to do the job:

@rem thanks to https://stackoverflow.com/questions/97875/rm-rf-equivalent-for-windows
@echo TEP - Terminate with Extreme Prejudice (die, die, die)
@echo off
setlocal
SET /P AREYOUSURE=Are you ABSOLUTELY SURE you want to irreversibly delete folder '%1' [y,N]? 
IF /I "%AREYOUSURE%" NEQ "Y" GOTO abort
set emptyFolder=%TEMP%\tep_%RANDOM%%RANDOM%%RANDOM%
mkdir %emptyFolder%
@REM robocopy will mirror an EMPTY FOLDER into the target
robocopy /mir %emptyFolder% %1
rmdir %emptyFolder%
rmdir %1
goto exit
:abort
echo Nothing done.
:exit
endlocal

The only thing I’ve found that this won’t delete is open files.