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The Renaissance Of SLR Technology.

The fitting replacement for DAT technology

Magnetic tape has successfully addressed IT market requirements for data backup by providing a secure, high storage capacity, removable media, at a low cost per MB/GB of recorded storage. Although the demise/displacement of tape has been predicted for years by various CD/DVD/competing removable technologies, tape remains king for serious backup of business data.

This article will focus on tape technology applicable to the SMB market. This segment consists of IT users who demand reliable low cost backup with a street price of $1500 or less.

The unit volume leader in the segment, DAT technology, has reached a pinnacle with the DDS-4 format. The storage capacity demands for the SMB user are continuing to grow. But DAT technology is now so highly leveraged that DDS-5 products may never materialize. Further enhancements to DAT storage capacity and to a lesser extent transfer rate require either "new inventions" or are at the "cutting edge" of tape recording technology.

The truncated capacity of the current DDS road map leaves room for other tape technologies to absorb DAT customers whose capacity requirements have outgrown the current DDS roadmap and capture "new" customers in the SMB sector. There are currently at least eight available technology families vying for market share in the SMB segment.

The popularity of DAT has set some consumer expectations for price point, performance, form factor, and availability of family extensions such as automation. In order for a different tape technology to successfully capture the DDS market space it must meet all consumer expectations in these areas as well as effectively address recent computer trends such as "RAS" (Reliability, Availability, and Serviceability).

The customer will be looking for a technology with plenty of headroom; with per drive disk capacities in the 73GB range the customer will look especially close at capacity/performance futures. The customer will require a tape technology that can be cost effectively deployed today and which promises a cost-effective future.

A Little Tape History

In 1990 the disk industry was on an exponential growth path (and still is) in terms of capacity and performance; however tape technology was struggling to keep pace. QIC committee companies were no longer able to bring competitive devices to market easily. Each company had different expertise mixes related to recording. Some companies were good at high track density, some at high bit (linear) density, some specialized in multiple data channels.

Depending on how a new format was composed particular companies may have been granted competitive advantages based on their expertise. In this environment it was difficult to agree upon development standards lest one company enter the market before the competition.

In the early 90s companies were forced to evaluate basic recording techniques and make choices. These choices were based on which format would best suit future requirements for extensions to capacity and performance balanced with "in house engineering expertise". Consideration was given to track density, track pitch, available media area, recording format (helical scan vs. linear/longitudinal tracks), tape speed, and system dynamics.

Some companies elected to take devices from the consumer sector (8mm Video and DAT audio), which already had relatively high recording density due to high stripe pitch (track density) and adapt them for data storage usage. These companies created formats specialized for data recording, added enhancements for ECC, and computer interfaces (SCSI) to the devices.

Still others adopted existing media styles and created new basic formats. DLT (then in the DEC world) has its heritage from the mainframe "3480 square tape". Tandberg Data elected to stay with the QIC data cartridge style.

Exabyte (then a start up) was the only company who chose 8mm video as a base technology; many manufacturers developed drives based around DAT drive technology. DAT companies included Aiwa, Archive (Conner/Seagate), Hewlett Packard, RByte, Sony, and WangDAT. Thus diversification in the computer backup tape industry was born in earnest.

As we enter the 21st century the tape technology choice war is still going on. The last three years have seen introductions for new helical devices (AIT, VXA-1) as well as linear (Onstream, LTO family) drives.

It Starts With The Technology

Core Technology: A major portion of the basic tape unit cost and performance capability relates to the recording technique chosen. Regarding mechanism cost, all tape drives require a SCSI interface, Data Buffer, Hardware Data Compression, and Micro-controller system. It is safe to say cost levels for these components between the various technologies are similar.

Where the cost differences between the technologies come in to play is in the components used directly for the recording process such as the magnetic head(s), Electric motor(s) required, actuators required, and precision mechanical components to implement the recording format. In these areas the technologies vary widely.

Helical Scan Products: (track is recorded diagonally in "stripes" across face of longitudinal tape) All current helical scan products utilize a dual hub driven cassette/cartridge and a rotating multi-channel recording head. A separate motor is required to control each tape hub as well as one for spinning the recording head (3 electric motors).

In addition, the tape guidance path on all helical drives is contained fully inside the drive (requiring precision mechanical components/guides) adding complexity/cost. Generally two other actuator motors are required for cartridge housing, load/unload, and tape threading/wrap around the head.

As far as capacity futures are concerned DAT, 8mm, AIT, and VXA-1 helical scan products have less available total tape area then TRAVAN, SC50, SLR, and DLT tape formats. While the smaller cartridge size is "sexy" it is a liability when it comes to ultimate data storage capacity.

Linear Recording Products: (tracks are recorded parallel with face of longtitudial tape) In linear drives the basic recording technique is similar between TRAVAN, SLR, SC50, and DLT-1 drives (there are variations in recording density/encoding, track pitch, and number of parallel channels). However there are differences in how the tape is handled between the DLT cartridge based drives and the others.

The larger recording surface provided by the linear technology drives allows for greater storage capacities in linear products at equivalent data packing densities. Linear recording technique also allows the scaling of data transfer rate based upon addition of recording channels in parallel. It is more difficult to substantially increase the transfer rate on helical formats by addition of parallel channels. Limitations come into play related to relative head to tape speed with helical scan drives where the tape and the head are moving.

TRAVAN, SLR, OnStream SC50 utilize cartridges which contain both tape guidance components and a portion of the tape drive system. While this makes for a more complex cartridge, the benefit is the tape drive mechanics required to make use of the cartridge are simplified. An added benefit of this system is less probability of having interchange problems between different drives. In drive styles which fully contain the guidance mechanics in the drive, it is possible to have minor variations in track placement between drives (leading to data interchange problems). The TRAVAN, SLR, OnStream SC50 drives only require one motor to drive the tape, 1-2 actuators to move the head, and one motor to load/unload the tape.

The media surface area with these technologies is far greater than either DAT or 8mm drives with SLR style tapes being second to DLT type cartridges in terms of overall recording area.

DLT1 style drives use a DLT tape IV cartridge. This type of cartridge provides the ultimate media area (and thus the most storage capacity for equivalent packing density). It does this by filling the entire cartridge "real estate" with tape on one single reel.

All DLT style drives require a take up reel located in the drive. This means that DLT drives require two drive motors for tape motion. In addition the tape cartridge contains no tape guidance facility; thus the drive must contain the precision tape path. This contributes additional cost and also is more susceptible to the interchange errors mentioned previously.

The take reel in the drive also means DLT1 style products take longer to load and unload tapes. In a load situation the tape must be threaded through the drive and wrapped around the take up reel, some tape must be wound before tape tension can be established. In unload situations the tape must be fully rewound back into the cartridge before the cartridge can be removed. These operations take time--more than any of the other technologies.

The Benefits Of Tandberg Data Heritage

Tandberg Data has been a pioneer in computer data cartridge formats for the last 20 years. They have produced over 2.5 million tape drives based on SLR technology. Their current product range is their second-generation SLR (Scalable Linear Recording) product family. Tandberg continues to ship SLR drives in high volume (250,000 in 1999).

This family uses advanced technologies including VR2 encoding for additional data density at a given magnetic density, dynamic servo tracking for additional reliability, shock resistance, and capacity, and an engineering methodology where data formats on tape are created to provide maximum capacity/performance with minimum interchange "baggage".

So how is SLR technology positioned to be the new king of the hill in the SMB sector? Take a look at it translated in terms the average user will understand.

Price Point: SLR technology, which requires fewer motors and less precision mechanical parts content than helical scan products or DLT type drives, is positioned well for aggressive market pricing.

Product Family: In the current environment the user would like to specify a product family which has a future. The SLR product family already has 2 products available beyond the 20GB product category and offers native 50GB/5MB/sec drives today. SLR drives have cost effective autoloader and library technology available today as well.

Performance: SLR technology has short media load/unload times, supports partitioning of media for QFA directories required by some software packages (just like DAT), and all SLR cartridge formats have special features for improving block seek times. In addition higher capacity drives support automatically adjusted multiple transfer rates, optimizing throughput. The advanced VR2 encoding means greater storage capacity and higher transfer rates with less data channels.

Reliability: The current SLR products dynamically adjust recording parameters to insure maximum interchange capability and long service life without problems. Drives have advanced diagnostics and continually demonstrate less than .05% field failure rate.

Support: SLR technology has broad software support. All technical documents and current firmware images are downloadable off the Internet. Tandberg Data offers toll free technical support as well.

Futures: The SLR formats hold other advantages as well, with special features in recording format for tracking media by individual serial number, actual media usage, and media performance, as well as drive performance.

Tandberg Data will implement advanced management information features this year that will allow the user to know the "health" of their drive as well as the media they use with it.

To Conclude

The SMB tape sector is full of alternatives but weigh your choices when it comes to malting a selection.

TRAVAN NS drives may prove to have too limited a roadmap, are not considered robust enough for serious IT use, and have no automation support

OnStream and Ecrix are new tape technologies and although they offer unique features and aggressive pricing their volume success is not assured.

The Mammoth and AIT products will be difficult to cost reduce to meet SMB market price expectations

For DLT1, it will be difficult to match the ultimate price expectations of this market. Although DLT drives dominate the enterprise market space the technology may not scale well.

SLR drives, with an installed base of 900,000 drives, 14 years of product advancements, and a "next step" product with 2X the capacity and performance of DDS4 available today, are the logical choice.

Gregg Ormsbee is the business development director at Tandberg Data (Simi Valley, CA).

The editors invite other claimants to the DAT space to make their
Fig 1
 Price Point
 Model closest to DDS4 parameters-Q4 2000
 Drive Model/Maker Drive
 DDS-4 Composite $1,083
DLT1/Benchmark Storage $1,199
 VXA-1/Ecrix $777
 Mammoth-1/Exabyte $2,414
 SC50/Onstream $683
 AIT-1A/Sony $1,832
 SLR40/Tandberg $983
 NS20/Tecmar $391
 Performance
 Drive Model/Maker Media Autoloader Capacity
 (Native)
 DDS-4 Composite $26.71 $2,691 8/1 20GB
DLT1/Benchmark Storage $66.59 $3,933 7/1 40GB
 VXA-1/Ecrix $64 $3,218 15/1 33GB
 Mammoth-1/Exabyte $49.06 $5,816 7/1 20GB
 SC50/Onstream $41 N/A 25GB
 AIT-1A/Sony $74.14 $3,455 4/1 25GB
 SLR40/Tandberg $51 $5,301 8/1 20GB
 NS20/Tecmar $30 N/A 10GB
 Drive Model/Maker Transfer Load Time of
 technologies
 Rate (Native) relative to DAT
 DDS-4 Composite 3MB/sec
DLT1/Benchmark Storage 3MB/sec ++++
 VXA-1/Ecrix 3MB/sec +
 Mammoth-1/Exabyte 3MB/sec +
 SC50/Onstream 500K-2MB/sec +
 AIT-1A/Sony 3MB/sec =
 SLR40/Tandberg 3MB/sec +
 NS20/Tecmar 1MB/sec +
 Family range
 Highest
 Capacity
 Drive Model/Maker Access Time drive in family
 of technologies available
 relative to DAT today (native)
 DDS-4 Composite 20GB
DLT1/Benchmark Storage +++ 40GB
 VXA-1/Ecrix + 33GB
 Mammoth-1/Exabyte + 20GB
 SC50/Onstream +++ 25GB
 AIT-1A/Sony - 25GB
 SLR40/Tandberg ++ 20GB
 NS20/Tecmar +++ 1OGB
 Highest
 Transfer
 Drive Model/Maker rate available
 rate with drive
 today (native)
 DDS-4 Composite 3MB/sec
DLT1/Benchmark Storage 3MB/sec
 VXA-1/Ecrix 3MB/sec
 Mammoth-1/Exabyte 12MB/sec
 SC50/Onstream 2MB/sec
 AIT-1A/Sony 6MB/sec
 SLR40/Tandberg 5MB/sec
 NS20/Tecmar 1MB/sec
Fig 2
 Technology
 Motors
 contained in
 drive relative to
 DAT (adds cost/
 Basic Recording decreases
 Drive Model/Maker Technique reliability)
 DDS-4 Composite Helical 3
DLT1/Benchmark Storage Linear -
 VXA-1/Ecrix Helical =
 Mammoth-1/Exabyte Linear =
 SC50/Onstream Linear --
 AIT-1/Sony Helical =
 SLR40/Tandberg Linear --
 NS20/Tecmar Linear --
 Precision
 Mechanical
 Actuators Content
 contained in contained in
 drive relative to drive
 DAT (adds cost/ (adds cost/
 decreases decreases
 Drive Model/Maker reliability) reliability)
 DDS-4 Composite 2 High
DLT1/Benchmark Storage - -
 VXA-1/Ecrix = =
 Mammoth-1/Exabyte = =
 SC50/Onstream - --
 AIT-1/Sony = =
 SLR40/Tandberg - --
 NS20/Tecmar - --
 Leverage
 FTPI
 Tracks/Stripes less flux transversals
 per inch per inch for an
 less is better (allows equivalent
 for growth by adding capacity are
 Drive Model/Maker additional tracks) better
 DDS-4 Composite 3,870 122
DLT1/Benchmark Storage --- +
 VXA-1/Ecrix - ?
 Mammoth-1/Exabyte --- -
 SC50/Onstream ---- ?
 AIT-1/Sony -- +
 SLR40/Tandberg ---- ++
 NS20/Tecmar ----- -
 Media Area
 Data Channels more is better
 less channels for (allows for
 equivalent additional capacity
 transfer at equivalent
 Drive Model/Maker rate is better track/bpi densities
 DDS-4 Composite 4
DLT1/Benchmark Storage - ++++
 VXA-1/Ecrix = +
 Mammoth-1/Exabyte = +
 SC50/Onstream + ++
 AIT-1/Sony = +
 SLR40/Tandberg = +++
 NS20/Tecmar - ++
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Article Details
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Title Annotation:Company Business and Marketing
Author:Ormsbee, Gregg
Publication:Computer Technology Review
Geographic Code:1USA
Date:Dec 1, 2000
Words:2435
Previous Article:Demystification Of Tape Technologies.
Next Article:ask THE SCSI EXPERT.
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