Back Up Storage With The Latest Generation Of Magnetic Tape Cartridges.

Each year data centers experience an increase of 50-100 percent in the amount of data to be stored. The cumulative effect of these storage increases has been an increase in the number and complexity of data storage systems. While the goal of every data center is to bring the cost of storage down, all these innovations in data storage, data management, and data security make it difficult for traditional data center management to understand the advantages and disadvantages of each new system, creating a greater risk of costly wrong decisions.

An analysis of data storage indicates a large percentage of the costs associated with storage results from the deployment and management of stored data. Management priorities and access time control storage costs. Storage costs range from around $0.02/MB to $0.30/MB. They are application-sensitive with certain installations providing very fast access to data at a premium cost.

In many instances, migration to, or the addition of, a new storage scheme reduces storage costs. There is another way to achieve costs savings and avoid falling behind the eight-ball of storage technology. Many data centers have gone from just subcontracting maintenance to outsourcing their complete operation. New, emerging companies provide state-of-the-art data storage, the requisite infrastructure and the latest security innovations. Because they share their storage installation and services are shared among several clients, they are cost-efficient for each client.

Outsourced or inhouse, to leverage their enterprise's data, data centers must consolidate hardware and software into fully compatible high capacity storage systems that offer improved access and performance. These systems feature the new high-capacity tape-storage platforms. The days of multiple hardware platforms and operating systems working with multiple databases, software configurations, and storage media within one enterprise are drawing to a close.

Media conversion services exist to convert data from one format to another, or from many formats to one standard format, but older tape media formats are not discarded easily. The federal government, for example, is still using and purchasing 800 BPI reel-to-reel tapes.

Now more than ever enterprise storage needs a high capacity, low cost storage medium. Magnetic tape with its new generation of tape cartridges maintains its position as the low cost removable medium best suited to the ever-growing need-storage in the next decade.

Today 100GB (or more) per tape cartridge is the storage capacity of current generation magnetic tape cartridges. Yet, everyone still wants instant access to their data.

To reduce access time, various approaches like increasing the tape speed and parking the media in the middle of the tape pack have been tried. Virtual tape storage (VTS), which has quickly become prevalent, in combination with Fibre channel connections and centralized shared storage has in fact created widespread improved access time to data. VTS has also boosted the average removable storage unit capacity utilization from around 30 percent to 85 percent, saving on space, energy costs, and media costs.

Perhaps one reason for the continued existence of older backup storage schemes is the reliability of tape storage. Rarely is the age of an MTC or even tape reel checked before being used for the archival storage of vital company data needed for ten or more years; today this means that one could be using a 15-year-old 3480 MTC to do that. Management has come to rely on securely backing up data on media, which historically only cost a few dollars per unit.

A Lack Of Standardization In MTC Formats

Magnetic tape cartridges are attractive to enterprise storage because they offer reliable low-cost storage. They have everything going for them except interchangeability. There are no industry-wide standards to allow the easy transfer of data from one system to another. This lack of MTC standardization forces data centers to choose among different manufacturers.

As storage capacities and the amount of data to be stored grow, the rapid accessibility of data across the enterprise becomes increasingly important. Unfortunately today, the new magnetic tape cartridge backup and archiving storage systems are characterized by the technically different proprietary standards of each system's manufacturer. Even Linear Tape Open, LTO, is somewhat proprietary because it is not standardized globally and because the LTO consortium forces potential manufacturers to pass rigid qualification tests. Relatively speaking however, LTO allows the market to benefit from competition among its manufacturers., This is not the case with some of the other products where, to satisfy multi source requirements, there is more than one source, but the overall supply is carefully controlled.

The hardware from the drive manufacturers is positioned to cover various market segments. They differ in head design, search speeds, and characteristics/interface, i.e. from low cost/data rate to high data rates (7.5MB/sec30MB/sec).

Eventually they will force users to choose one standard in order to achieve the full benefits of leveraging data across an enterprise. The question is, will the user community accept this structure? Until recently, enterprise storage users were contending with perceived Y2K challenges, which caused users to be less willing to jump into new, relatively unproven tape technologies during that critical period of backup. Y2K preparation made users more receptive to refinements of well-established mainframe tape technologies. Now, in the wake of Y2K, data centers must embrace proprietary MTC standards to achieve the efficient leveraging of data that is necessary to their enterprises' strategic use of information and overall competitiveness.

Contemporary MTC Characteristics

The development and refinement of the half-inch MTC medium has kept pace with enterprise computing's evolving and growing storage needs. And, the familiar MTC medium promises further advancement. These are some current improvements, characteristics, and considerations.

Cartridge Memory.

Computer chips are embedded into the shell of some new generation MTCs. With this CM device, the drive can communicate with the cartridge via a non-contact passive radio frequency signal and establish communication with a nonvolatile memory (EEPROM) before the cartridge is inserted into the drive. This saves time by initiating calibration and other media/drive initialization tasks like transferring the media error map etc. that are required before one start of the cartridge to store or retrieve data. AIT and LTO cartridges have this feature.

Linear/Helical.

In enterprise storage, linear recording is the dominant format in all half-inch tape technologies including 3480/90, 9840, DLT, 3590, and T9940 as well as the 8mm 3570. There are very few helical systems in enterprise storage. The server and Network segment is dominated by the linear-tracked LTO and DLT cartridges. AIT and Mammoth are some of the helical scan products in this market.

High capacity MTC Security Practices.

One of the consequences of these high capacity cartridges is the practice of double/mirror backups. Apparently data center managers are not comfortable with having large amounts of data on a single cartridge. Some estimates put the value of 100GB of enterprise data at one million dollars. So if there is a problem with one of these new high capacity cartridges or the drive and a block of data is not retrievable, the consequences can be serious. Another security consideration for the high capacity MTC is, a cartridge holding 100GB of data can be easily concealed.

A New Generation of Sensitive Media

To meet the need for higher capacity MTCs, manufacturers developed a thinner, smoother tape medium and adapted servo-track technology, which had been in use on hard disc drives for many years, to tape drives. A thinner tape allowed more feet of tape to be wound on the same sized cartridge thereby increasing the cartridge's storage capacity. A smoother tape facilitated an increase in bit density allowing more data to be stored in a given square area of tape. This was accomplished by increasing the number of tracks and making them thinner on the smoother, more dense tape. Servo-track technology positions the head accurately on the tape service. At a high number of tracks (387 on the LTO Ultrium) it also requires more intimate contact between the drive head and the media, as well as a consistently smooth surface.

To illustrate, one of the main differences between the two competing formats, LTO Ultrium and Quantum Super DLT, is the servo-track system. Ultrium has a fourth generation IBM servo system with 500-micrometer edge-guard bands. The Ultrium tape has five prewritten servo tracks with four data areas between them. Each of the data areas contains 96 tracks written by an eight element head in a linear serpentine recording mode making twelve passes. The edge guard bands make the cartridge less sensitive to possible tape damage as a result of non-uniform tape pack wind, temperature shock, and transportation. SDLT on the other hand is using a new Laser Guided Magnetic Recording (LGMR) servo technology. The optical servo track is written on the backside of the tape.

To ensure tape surface quality, cleaning stations are installed on newer tape drives. For comparison, the 3490 cartridge had 36 tracks, while the 3590E cartridge has 256 tracks using servo-track technology.

A 3590E cartridge is also far more sensitive to temperature exposure and handling than the 3490. IBM had to create a different shipping box for the 3590E increasing its volume 2.7 times.

The same exposure and handling considerations have to be given to the new generation of 100GB-plus cartridges like LTO and Super DLT cartridges. Tape damage due to dropping and handling is a great concern. To eliminate any strain on the tape, the new LTO drives feature dynamic power down in the event of a power loss. Seagate has incorporated Fast Sense to monitor the incoming data rate from the host to reduce/eliminate any unnecessary tape stops, reversals, or jerking. Hewlett Packard has data rate matching which in essence performs the same function.

The sensitivity of the new LTO media has also affected the development of cleaning cartridges. Each drive manufacturer has its own cleaning cartridge that will only work in specific drives. This is accomplished by installing a CM chip (mentioned above) in the cleaning cartridge. Allowing the cartridge to acclimate to the computer room environment is also far more important with these products.

The SDLT camp has also realized the same problems and given great care in designing the SDLT cartridge and hardware to minimize physical damage.

Data centers must give more attention to drive maintenance and the care and handling of these high technology, latest generation cartridges because thinner media is far more sensitive to the tape path and environmental variables. Under the right conditions, these new products can remain durable. The EMTEC LTO Ultrium cartridge, for example, was developed for high use in archiving and storage environments. The metal pigment coating on a PEN (polyethylene naphthalate) base film ensures no data loss after 1,000,000 head passes or more than 20,000 short section passes under demanding conditions. To arrive at these numbers, EMTEC ran a statistically valid sample of tapes from different batches through more than 12,000 passes (full length of 100GB data) without failure.

High capacity magnetic storage for Enterprise Data systems and the Server/Network segment will continue to focus on magnetic tape in the next decade. New tape drives and MTC storage systems will have innovative features to reduce access time and increase performance. The storage capacity of magnetic tape will continue to grow exponentially. LTO/Ultrium specifications, for example, call for an 800-gigabyte cartridge by 2008. If one keeps in mind that 100MB data has an average value of one million dollars it is not surprising that mirror or dual backups will be a byproduct of these ever-increasing cartridge capacities.

Technically, the question will be how many exponential jumps in bits per inch (BPI) can metal particulate (MP) tape coating technology support. Metal (cobalt) evaporated (ME) media is most likely the next step, but will it have the needed mechanical properties we have gotten used to? And, ME's cost must come down. As bit density goes up and tape coatings become thinner, the tape surface will become smoother but still should be able to withstand the wear and tear of daily use.

Magnetic tape cartridges are small. They are removable. They are reliable and they are inexpensive. Their storage cost per megabyte is the lowest. These four simple reasons are why MTCs will remain the choice of data centers for backup and archiving for several more years.Leapfrogging proprietary technology and advancements have led to a market governed by proprietary standards. Currently LTO offers a possible path away from the continuation of proprietary standards into the foreseable future.

Gerrit Nijssen is the director of applications engineering at EMTEC DataStoreMedia, Inc. (Billerica, MA), the North Amen can subsidiary of the Germany based EMTEC Group, formerly BA SF Magnetics.

High Capacity Tape Options
Product    Tape Width  Recording  Tape Coating  Native Capacity
DD-2L      19 mm       Helical    MP            330 GB
DTF-2L     12.7 mm     Helical    MP+           200 GB
Super DLT  12.7 mm     Linear     AMP           110 GB
LTO        12.7 mm     Linear     MP++          100 GB
AIT-3      8 mm        Helical    AME++         100 GB
T9940      12.7 mm     Linear     MP            60 GB
AIT-2      8 mm        Helical    AME+          50 GB
3590E      12.7 mm     Linear     MP            40 GB
Product    Native Transf. Rte
DD-2L      20MB/sec
DTF-2L     24MB/sec
Super DLT  11MB/sec
LTO        15MB/sec
AIT-3      12MB/sec
T9940      10MB/sec
AIT-2      6MB/sec
3590E      14MB/sec
MP = Metal Pigment
AME = Advanced Metal Evaporated