Using DDS Tapes
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.
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).
And still more!
From: "Wilkins, Mark D." <firstname.lastname@example.org> 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.