DDS or Audio DAT tape?

Should I use DDS-1 computer grade or audio DAT tape?

DDS-1 (Digital Data Storage) 4mm tape generally comes in 60 meter (120 minute) or 90 meter (180 minute) lengths and is designed for "mission critical" computer tape backup.

The tape used for 60 meter (120 minute) computer grade DDS tapes and audio tape is basically the same (90 meter being thinner). Computer grade tape is taken from the center of the roll (before slitting), and must meet strict ANSI standards. The tape has a much lower BER (Bit Error Rate) than most DAT tape and is significantly more reliable. Unlike audio DAT tape, DDS tape is certified "error free".

DDS-1 may be used in place of audio DAT tape and is preferred by most people. DDS-2 and up can not be used as an audio DAT tape.

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Some more info on the subject:

                        Maxell Technical Bulletin 

                      4mm Data Cartridge vs. Audio DAT 

Maxell manufacturers digital audio tape (DAT) for audio use and
4mm data cartridge for computer back-up. Both products are premium
quality. However, 4mm data cartridge has certain advantages that
make it ideal for the demands of computer applications. 

1. 4mm data cartridge is certified to meet a rigorous minimum of
"drop outs" which are losses in read signal output that lead to
raw-bit error rates. DAT tape has no minimum drop-out requirements
because of the minor downside effect for audio use. Minimum drop-outs
are specified by ANSI in document X3B5/90-280 (2nd Draft). 

2. Maxell's 4mm data cartridges are manufactured in a class 10 clean
room to prevent invasion by any airborne contaminant such as dust or
smoke particles that can create interference between the sensitive
read/write heads and the ultra high-density data tracks. DAT tape does
not require class 10 clean room manufacturing. 

3. Maxell's 4mm data cartridge shells are made of a special anti-static
resin to prevent attraction of airborne contaminants. The cartridge
shell has also been specially modified to prevent jamming in computer
drives and auto loaders and is durable enough to withstand 15,000 
load/unload cycles. DAT tape does not require these modification or
adherence to these standards. 

4. Maxell's 4mm data cartridges now feature Safe-T-Lock, a new hub
locking mechanism that ensures proper tape tension and prevents 
mis-threading during the initial loading stage into the computer
drive. Audio DAT does not have this feature. 

5. Maxell's 4mm data cartridges are equipped with MRS (Media Recognition
System) in compliance with the DDS Group. MRS allows 4mm drives to
identify data grade and reject audio tape. Accordingly, Maxell's 4mm
data cartridges bears the DDS approved logo. 

6. Maxell's 4mm data cartridges are backed by a lifetime warranty,
are guaranteed to satisfy and are fully supported by a toll-free
hotline (1-800-377-5887). Maxell's engineering department is available
to assist in any way and will attempt data recovery at no charge. 
Customers using DAT for computer use do so at their own risk and have
limited recourse). 
                    

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And still more!

From: "Wilkins, Mark D." <mark.wilkins@alcoa.com>
Subject: "Success with DDS Media"
Date: Wed, 28 May 1997 16:52:11 -0400

Just cleaning out the library at work and came across above-named 
publication from HP.  Part # C1500-90911, Edition 1 April 1991 for those 
who care.

22 pages of mostly painfully obvious info ("do not touch the tape inside 
the cassette", etc) but a few interesting items.  I apologize for the 
length of this message, but wanted to pass along some info that I thought 
was relevant to a few recent discussions.

Keeping in mind that this is in the context of computer data storage and 
that they want you to use HP tapes in HP drives connected to your HP 
computer, witness the following quotes:

p.14 "DDS and DAT Cassettes"
It is often thought that all DAT and DDS tapes are of a standard that can 
be used for computer data storage.  This is NOT the case.

The way tapes are used for data storage is fundamentally different from 
audio use.  Audio tapes only play in streaming mode; that is, the drive 
reads the tape continuously.  It does not go back and try a piece of tape 
again if it has trouble reading it.  As a result, repositions (sequences of 
stop-rewind-play) are very infrequent.

In data storage use, however, repositions are far more frequent, 
particularly if the host computer is only capable of slow data transfer. 
 In such a case, the drive is constantly having to stop or reposition while 
waiting for the drive to transfer more data.  Even when the host is fast 
enough to maintain streaming, if the drive has difficulty reading a section 
of tape, it will try the section again, involving at least one reposition. 
 Fast-searching for data can also cause several passes over an area of 
tape.

These repositions are the greatest cause of physical strain on the tape. 
 Because computer data storage involves so many more, it is vital to ensure 
that the tapes can stand this extra strain and will have a reasonable 
working life.

In order to provide this extra guarantee of quality and ruggedness for 
computer use, a standard for DDS media was developed.  This stipulates more 
stringent mechanical, environmental, reliability and durability 
specifications than the DAT standard.

For these reasons, it is vital that you use only properly certified DDS 
tapes in your drive, not DAT tapes which are only tested for audio use.

p.21-22 "Common Questions and Answers"
Q: How often should I clean the tape drive heads?
A: You should clean the tape heads after every 25 hours of use, or if the 
Caution signal is displayed.  Only use the HP Cleaning Cassette to clean 
the heads.
Q: How many times can I use a DDS cassette?
A: The recommended number of tape passes is 2000. This is equivalent to 
approximately 300 insertions of the cassette, given that on each insertion 
the tape is likely to pass the heads an average of six times.
Q: For how long can I archive tapes?
A: Ten years is the maximum recommended storage time for DDS cassettes. You 
should give the cassettes a full pass in the drive at least once a year 
during storage to prevent the tape sticking.
Q: Can I use DDS cassettes for audio?
A: Yes, DDS cassettes will work in DAT players.  DDS cassettes are 
certified to a higher specification that DAT cassettes, so while DDS 
cassettes can be used for DAT, do not use DAT cassettes in DDS-format 
drives.