Long term backup data

frogglegs used Ask the Experts™
What is the best backup for archival purposes...Can someone give me references or details between different storage mediums...cdr, hd, flash drives, tape...etc..

Cost is somewhat of a consideration as well...
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Technology and Business Process Advisor
Most Valuable Expert 2013
I have writen up a lengthy article on the topic of backup which, among other things, addresses this topic.

In short, Tape is the best medium available for long term storage.

I agree with leew.  While tape archival is far from perfect, it's long-term characteristics and decay mechanisms are well understood.  All other means are far too new to have such a track record.

Fact of life, fact of nature. Plus and Minus always try 'to find' each other and make zero.
Any magnetic based media is going to degrade over time.
Hard drive, floppy, zip, tape, others,,, magnetic based.....
DVD or CD is not magnetic and will live longer without becoming corrupt but it's a more painful backup process.

I recommend a hybrid backup system/procedure.

I recommend doing the backup onto tape but then backup the tape onto a recordable DVD or CD.
This way if (and when because it will) the tape goes bad you can simply recover the backup from the optical media back onto a tape.

To make life easier have a basic (older, inexpensive, left over from last upgrade type thing) system around to do the tape to optical backup to optical. This way the 'work' system isn't busy when you backup your backup.
Better yet. If this is critical data make two copies of the optical media and store them in different physical locations.
[ Copy at the office, copy at the house - kind of thing. ]

Top Expert 2005

I'd say either tape or ONE-TIME (not "RW") optical media.

There's more history with tape, but the media makers say optical media can last many, many decades to centuries if properly written and stored.

I have hundreds of 8-inch floppy disks from the 1970's and they are still completely readable at more than a 99% level, and as antique computer are a hobby of mine, I talk to other antique computer users, and we all find that 30 years is no problem for 8-inch floppy diskettes that were stored properly.  Tape uses the same basic type of magnetic medium in a different format, and has been around for as long, thus looks good for decades (but probably not centuries).

I also have CD-R going back to 1995, and it's still fine if the media was good and it was well recorded (I can tell NOW, a decade later, which media was good (most of the name brand stuff was) and which drives were good).  However I do think that there are more people with optical drives that "write lightly" (don't fully burn the media) than anyone knows.  And I don't yet have a good feel for DVD media or, in particular, DL DVD media (dual layer).
The only "BEST" is the one that works for you.  I find tapes an antiquated inefficient debacle of yesteryear, but some people who live in the past think they are great.  I would go with nothing but fast IDE drives on a network storage server, backed by DVD archives of the old backups of systems.  But each person has their prejudices.  Some are behind the times, others are up with the leading edge.  You will have to research it and find what technology you can cope with, many cant face the future of backup.
Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013
Do the math - if you need to backup long term, hard drives will cost you FAR, FAR more than tape.  I find scrathcyboy's comment to be shortsighted at best.
I dont think that hard drives will be more expensive...

If you want it on tape you will have to pay for the tape drive, the backup software and the tape itself. In 15 years time you will probably find it difficult to reinstall the software on the new 128 / 256 bit operating systems and you will find it hard to get the hardware to function on the new PCs.

Instead buy 2 cheap IDE disk drives and back  them up on that. A couple of months ago I bought 2 320Gb drives for less than £200
Top Expert 2005

Here in the US, Best Buy was selling WD 320gb SATA drives for $99 (no rebates, either).

Hard drives are is a good choice for a single backup, but it's hopeless if you are trying to keep an archive of {daily, weekly, monthly} backups.  Personally, I prefer DVD for backup, but many are not comfortable with that for a variety of reasons.  In a year or two, that will transition to HD DVD or (I personally hope) Blu-Ray, with a capcity of 50 gig or more per disc.

Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013
Ok, let's do the math.

You need to store backups for at least 5 years.  Each backup is 300 GB (which seems kinda low for any business of a reasonable size).

250GB Drive = $75 at newegg. Cost/GB = 30.00 cents (best cost/GB available I've seen; the bestbuy drive for $99 is 31.25 cents per GB).
400GB LTO Tape = $85 at newegg.  Cost/GB = 21.25 cents

Each tape will probably hold about 500 GB with compression (Real life, I'm not talking advertised), each hard drive, maybe 300 GB.
Tape w/compression = 17 cents/GB
Hard Drive = 25 cents/GB

An LTO3 Drive at newegg is $3250.

A Hard drive adapter (not an enclosure) - something like a combodock from www.wiebetech.com, is about $175.  Over 5 years where you have FULL backups every two weeks (26 per year) (which also seems kinda low - most do fulls every week), that's:

26 Annual Backups x 300 GB per full x 5 years = 39000 GB or 39TB.

with tape at 17 cents per GB that's $6630 for the media
with drives at 25 cents per GB that's $9750 for the media.

TAPE: 6630 tape media + 3250 tape drive = $9855 5 year cost
HARD DRIVES: 9750 drive media + 175 wiebetech device = $9925 5 year cost.

Double the frequency of backup to the more common weekly schedule your drive costs skyrocket while the tape costs aren't so bad:
TAPE: 13260 tape media + 3250 tape drive = $16510
HARD DRIVES: 19500 drive media + 175 wiebetech device = $19675

I love using hard drives instead of tape - for small, non-long term situations - read my link - but for long term storage, tape is best from a cost perspective and a storage perspective.

Gary CaseRetired
Most Valuable Expert 2013
Top Expert 2009
Let's dissect your question a bit:

"... What is the best backup for archival purposes..." ==> This really depends on the scale you're talking about.  The discussion so far assumes a typical large-scale business with hundreds of gigabytes or terabytes of data.   For these cases, the answer is clearly tape (as already noted).   But for a smaller business the answer is less clear (more in a minute).

"... Can someone give me references or details between different storage mediums...cdr, hd, flash drives, tape...etc.." ==>  There are many discussions on the web r.e. the various mediums (just "Google" for the media you want to research -- e.g. "LTO tape life").   In general, you'll find that high quality optical medium have the best rated life (50-100 years), while tape is rated for 15-30 years.  HOWEVER, I'd still suggest tape is a better choice for longevity because the rated life does not consider the issue of handling of the media.   It is easy to mishandle optical media (fingerprints for example), while tape is very well protected.   Of the items you've listed -- CDR, HD, flash drives, & tape --> I would not use CDR (DVD-R is a far preferable optical medium);  Hard drives have both the cost disadvantage noted earlier in this thread, and also have the potential for drive electronics failure;  flash drives are not a good choice as they have relatively low capacities and a short rated longevity (typically 10 years rated data retention); and tape has already been discussed.

"... Cost is somewhat of a consideration as well..." ==>  The earlier discussion of cost did a good job of comparing tape vs hard disks.   It omitted the cost of optical media, which makes sense IF the backup you're referring to is for a large scale system.   For completeness, however, it should be noted that the lowest cost, and the longest rated longevity, is to use high-quality DVDs.  You can buy top-quality DVD blanks (Taiyo Yuden) for as low as $0.38 each ==> a cost of 8 cents/gigabyte.  For small businesses with limited data volume it is not uncommon for backups to be relatively low numbers of gigabytes;  in those cases, it MAY make sense to use DVDs, possibly in conjunction with a hard drive backup.   As I noted earlier, it really depends on the scale of the backup.   Clearly if the backups are < 4.7GB (a single DVD) then the best solution is to use DVDs.   If the backups are larger, but still modest, you may want to do daily backups to a hard drive, and weekly backups to a set of DVDs (IF the # of DVDs required is small).   Note also that you can use dual layer DVDs to increase the capacity to 8.5GB/blank at a cost of 20 cents/gigabyte.   But despite the cost and longevity advantage of DVDs, I agree that tape is the backup of choice if the scale of the backups is large enough that the number of DVDs required is more than just a few (how many depends on the user -- and whether or not it's important for the backups to be fully unattended).

Regardless of the media of backup you might consider using additional Reed Solomon error correcting blocks as extremely effective additional protection against data corruption in time.  That would be far more effective than making duplicate backups.  You can obtain a nice free program to do the job at http://www.ice-graphics.com/ICEECC/IndexE.html .  Mode 1 and Mode 2 Type 1 CD recordings already contain very effective Reed Solomon correction (2352 bytes recorded for 2048 bytes of data), but you can use the referenced program to further protect your data.

Here I use a mixture of hard disks, CDs and DVDs for long term backup and would never consider again using magnetic tape.
I would not go the hard drive route for long term backup. Hard drives are subject to failure (otherwise why was RAID invented). Also buying "cheap" hard drives can be asking for trouble too. Hard drives are good for short term quick access but with some danger due to failure. Regarding tapes, I have had some where it writes and verifies perfectly but some time later it can't be read.  I agree that CD or DVD is the best for long term.

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