Best Long-Term Backup Storage Media

backup

Rumors say CDs and DVDs won't remember your data longer than ten years. Are there backup media that do better?

Best Answer

Hard Drives. Space is dirt cheap these days, you can grab a few TB worth of internal hard drives at a fairly low price. Even external hard drives aren't too expensive.

Paper

Other than archival ink on archival paper in sealed storage, no current medium is proven to last an average 100 years without any sort of maintenance.

Archival Paper

Older papers were made from materials such as linen and hemp, and so are naturally alkaline. or acid free, therefore lasting hundreds of years. 20th century paper and most modern paper is usually made from wood pulp, which is often acidic and does not keep for long periods.

Archival Inks

These permanent, non-fading inks are resistant to light, heat and water, and contain no impurities that can affect the permanence of paper or photographic materials. Black Actinic Inks are chemically stable and feature an inorganic pigment that has no tendency to absorb impurities like other ink pigments can.

Redundant storage

Torvalds once said

Only wimps use tape backup: _real_ men just upload their important stuff on ftp, and let the rest of the world mirror it

Which suggests you should not rely on a single copy on a single medium.

Not magnetic media?

http://www.zdnet.com/blog/perlow/the-bell-tolls-for-your-magnetic-media/9364?tag=content;siu-container

Typical example of irretrievable degradation of magnetic media.
Issues of hardware and software (and data formats)

Not specialized systems

In 2002, there were great fears that the discs would become unreadable as computers capable of reading the format had become rare and drives capable of accessing the discs even rarer. Aside from the difficulty of emulating the original code, a major issue was that the still images had been stored on the laserdisc as single-frame analogue video,

http://en.wikipedia.org/wiki/BBC_Domesday_Project#Preservation

Long Term Personal storage

http://www.zdnet.com/blog/storage/long-term-personal-data-storage/376

both the media AND the format can become unreadable.
print on acid-free paper with pigment inks and store in a cool, dry and dark place.
The first problem is picking data formats for maximum longevity.
Avoid using proprietary formats
USCSF is transferring all their original tapes - many in now-obsolete formats like BetaSP and VHS - to the 75Mbit motionJPEG2000 format

Is it normal for CDs/DVDs to decay over time, and what can we do about it

Probably preaching to the choir here, but this is experience gained after a couple decades of using the darn things. My first drive was a really expensive SCSI interface 1x CD-R. That $250 you pay for a really good manufacturer now? Pfft! I could buy six now for what I paid for that thing. Ouch!

Use a quality drive to produce the disk
Use a quality disk manufacturer (Mitsubishi, JVC, Sony) and as fresh a batch of disks as you can get.
Make sure the disk surface is clean before inserting into the drive
Slower burn speed is supposed to produce larger dots, verify data after burn
Multiple copies of important data is a "Really Good Idea™"

Also:

Time will degrade the write-ability of the dye layer, slow burn speeds will not make up for this, use as fresh a disk as you can get.
Heat will degrade the dye used in the writable layer.
Ultraviolet light will degrade the dye used in the writable layer.
Moisture can get through the label side coating and attack the aluminum flash layer.
In certain environments, there is a sort of mold that will eat the label side of the disk, even on pressed disks.

The 20-30 year lifespan quoted for writable disk life was based on advanced aging tests, not real lifetime tests. Real life shows that a high proportion of written disks probably aren't much good after 10 years.

So the name of the game is "make multiple copies over several media types for long term storage" on rather static data. With multiple copies, there's a chance of recovery of the bad files.

The case is not so good if large databases are involved, a couple bad spots can render the whole database useless on a couple disks. Most backups have a lifetime of weeks, so this isn't as much of an issue, but for monthly backups, you may need to do refresh copies every so often if long term storage is a legal liability.