how good is the data reliability with 90s and 2000s media?

[David Hess]

If I were doing this, I would settle for archival quality DVD+Rs or BD-R disks or both and burn two or more copies on different media types or brands.  Some burning programs might allow doing all of the burns simultaneously to save time.  In an extreme case, I might use two burners and two different disks to make four variations; disks are cheap.

One trick I really like although it takes a little extra time is to create and include a massive PAR2 set on each burned disk along with the PAR2 executables and maybe any other archive program executables.

[thermistor-guy]

I don't know if it's the right area of the forum, I'd like to discuss about CDROM, DVDRAM, IomegaZip, MO-disks, tapes etc, and their data reliability
...
Say, about me, I don't usually need Terabyte, 4.5Gbyte of media is more than OK since I usually need to archive projects, composed by C/C++/Ada sources, followed by tons of pdf and EagleCAD and gEDA sources.
...

Verbatim's archival DVDs and CDROMs look reasonable:

http://www.verbatim.com/prod/optical-media/professional-optical/archival-grade-gold-dvd-r/ultralife/
http://www.verbatim.com/subcat/optical-media/cd/archival-grade-gold-cd-r/

[rsjsouza]

Since we are talking brands, I had used Nashua for my 5-1/4 floppies (more than 800) without skipping a beat and they lasted  about two decades.  Later I switched to 3M and Verbatim for 3-1/2 which are the disks I still have today ( about 100 )
Optical media was always the deep dark green TDK (until late 1997) where supply started to be scarce and we had to diversify. Verbatim dark blue had become our primary source and lasted well over he years, while Mitsui gold had several failed copies but I still have one standing the test of time. At a certain point we bought a bunch of Sony boxes - we lost several due to a weird plastic degradation we thought at the time was mold. Since this is a brand that was faked quite ostensibly in the 1990s, I still don't know if that was the reason or simply a bad batch.

[tooki]

thanks for your answers, guys, very appreciated 

I am in the process of building a new SCSI media-tower loaded with
- DLT8000 tape (IBM tapes)
- DDS4 tape (IBM tapes)
- CD writer (Plextor writer, Verbatim premium dry-CDs)
- DVDRAM
- micro, mechanical removable hard drive (CF2 Microdrive)
- common 3.5" mechanical removable hard drive (SCA-80)

I am duplicating my backups in different kind of media in order to have more probability to have them preserved.

Umm, so you’re looking to create new backups or archives on all those media?!

A far, far, far more practical solution is to back up/archive to hard disks — multiple ones. And then every few years, copy those to new drives.

[Circlotron]

And store your backup disks/discs in several offsite locations.

[tooki]

Exactly! I meant to say that and forgot!

[james_s]

There are also cloud (ick) based backup solutions. When dealing with vintage stuff the total amount of data is usually small by modern standards and one of the free accounts is probably adequate. Also there is not usually much in the way of important personal info so I don't worry too much about the security of offsite storage.

[legacy]

A far, far, far more practical solution is to back up/archive to hard disks — multiple ones. And then every few years, copy those to new drives.

yup, this is done by this machine; it saves data on a mirrored a set of common sATA hard-drives. It's physically located in Switzerland, about 400Km far from where I usually operate, but being a NAS it's accessible on the internet 

[legacy]

And store your backup disks/discs in several offsite locations.

precisely

[CatalinaWOW]

I have had relatively few failures of media of any kind, but have had some hard drives, CD-ROMs, ZIP disks and floppies fail.  Media failure has been less common than drive failure.  Which then gets to the heart of your problem.

If you want to read your data 10, 20 or 30 years from now you will need to assure that you have a reader operating.  Availability of new readers for purchase declines rapidly as the time scale increases.  It is virtually impossible to buy "new" floppy or ZIP drives now.  I expect the same problem to develop over the next decade or two for CD disks.

The only solution for long term data archiving is a plan to continually move the data onto new media as the technology moves along.  And this problem is why when this civilization eventually crashes (they all do), almost all of the knowledge we have assembled will be lost with it.