Durability studies of metal evaporated tapes in a linear tape drive: Role of head contour and tape tension

Magnetic performance of metal evaporated (ME) tape makes it a prominent storage media candidate for future data recording systems. However, the durability of ME tapes, limited by a number of tribological issues, is a major concern. A preliminary investigation on durability of ME tapes in a linear tape drive has been carried out. The effect of head contour and tape tension on the durability of the head-tape interface has been studied. An optical microscopy based technique has been used to measure the quality of factory-slit tape edges and after use in a liner tape drive. Debris distribution over the head surface at the end of the testing has been monitored. The ME tapes are found to be sensitive to both head contour and tape tension. Some desirable attributes of ME tapes required to improve durability are discussed.Financial support for this study was provided in parts by the membership of the Nanotribology Laboratory for Information Storage and MEMS/NEMS (NLIM) and Imation Corp.-Advanced Technology Program (Program Manager, Ted Schwarz, Peregrine Technology, St. Paul, MN), National Institute of Science and Technology, as part of Cooperative Agreement 70NANB2H3040. Steve Gavit of Segway Systems, LLC (Littleton, CO) provided the tape drive with single flanged guides with porous air bearings. The authors also express their gratitude to Peter Groel and Jonathan Griffitts (both of Mountain Engineering II, Longmont, CO) and Chris Goldsmith of Accutronics Inc. (Littleton, CO) for fruitful discussions and technical support for the Segway drive. The authors thank Richard E. Jewett and Todd L. Ethen of Imation Corp. for fruitful discussions throughout the study. The authors express their gratitude to Shashank Aggarwal of NLIM for providing the results of FEM of tape slitting.     

Vibration response due to lateral tape motion and impulse force in a linear tape drive

Next-generation, high track-density linear tape drives will require improved tape guiding and dimensional stability in order to achieve better performance and higher storage capacities. Drive vibrations, tape degradation, debris formation, and tape guiding all contribute to unwanted lateral tape motion, which can lead to write errors on the tape. Collisions between the guide and tape edge can be simulated as single-impact events by dropping a mass onto a lever situated below the bottom tape edge. The objective of this study is to evaluate the frequency content of measured lateral tape motion under various operating conditions. The effect of impact location and impulse energy is investigated in a static test where the tape drive is not in operation (tape is stationary). Next, a dynamic test is performed to study the effects of tape speed, tape tension, impact energy, and tape thickness. Finally a durability wear test is conducted to determine the effects of cycling up to 5000 cycles. Lateral tape motion is recorded and the power spectrum density of the signal is determined for each test. Additionally, optical microscopy is employed to quantify the quality of the tape edge after wear testing to investigate any correlation between tape wear and frequency analysis.Financial support for this study was provided in part by the membership of the Nanotribology Laboratory for Information Storage and MEMS/NEMS (NLIM) and Imation Corp.-Advanced Technology Program (Program Manager, Ted Schwarz, Peregrine Technology, St. Paul MN), National Institute of Science and Technology, as part of Cooperative Agreement 70NANB2H3040. The authors thank Richard E. Jewett and Todd L. Ethen of Imation Corp. for beneficial discussions throughout the study. The authors also thank Dr. Anton Goldade of Maxtor Corp. for invaluable advice, insight, and assistance throughout the study. The authors finally thank Walter Hansen, Steve McDonough, Shashank Aggarwal, and Tony Alfano of NLIM for various beneficial discussions and data processing skill.     

Comparative analysis and associated failure mechanisms of magnetic media in advanced linear tape drives

Flexible magnetic tape is widely used for data storage and archival, as future generation of tapes and drives will continue to increase overall storage capacities and data transfer rates. Tape portability, robust drive operation, longevity of magnetic media, and improved performance of head–tape interface under long-term use are required for magnetic tape to maintain a stronghold in the field of storage devices. Comparative studies were performed to investigate differences in performance of various cartridges in impact, tapes under long-term durability, and contamination of head–tape interface in advanced linear tape drives. A drop test was performed in which various cartridges were dropped from varying heights. Cartridge damage was recorded and indexed. Reinforced cartridge casing promotes good stability at low height impact, while casing significant plastic deformation in increased-height drops. Contamination and durability studies were performed in which debris generation, tape edge damage, tape cupping profiles, and error data was collected and analyzed for studies of head–tape interface. Most significant loose debris generation occurs as a result of wear at the tape edges, while adherent debris is related to tape binder system, and causes increases in drive error rate. Cleaning brushes have been incorporated into the design of drives to reduce the accumulation of all types of debris. A study was performed to determine the effectiveness of brushes on head surface cleaning. The use of brushes in drives was shown to be helpful in removal of both loose and adherent debris types. The effect of relative humidity at the interface was examined, and it was found that high relative humidity acts as a lubricant at the head–tape interface, helping to reduce tape wear. Low relative humidity can have differing effects on the interface performance, as it has shown to either increase or decrease debris accumulation, depending upon tape characteristics.     

Vibration analysis of axially moving magnetic tape with comparisons to static and dynamic experimental results

The demand for greater storage capacity is prompting the development of data storage tape with greater volumetric and areal density. As the data tracks on these tapes become narrower, minimization of the lateral tape motion (LTM) becomes more important to prevent loss of data due to read/write errors. In order to identify and minimize sources of LTM, a vibration model is developed which simplifies the tape drive to a fixed-fixed Euler-Bernoulli beam model with axial velocity. The effects of varying axial velocity, tension, free span length, and tape thickness were investigated. The calculated natural frequencies are compared to those obtained by both static and dynamic experiments. Effects of varying the length, tape thickness, and tension were studied in the static experiment while the effects of changing speed and tension were studied in the dynamic experiment.     

Lubrication of advanced metal evaporated tape using novel perfluoropolyether lubricants

In order to reduce the failure of advanced metal evaporated (AME) tape, novel perfluoropolyether (PFPE) lubricants, Z-TETRAOL and A20H, were deposited on an unlubricated AME tape. The degradation mechanisms of the PFPE lubricants applied on AME tape were studied using a mass spectrometer in high vacuum. The durability of various lubricants was compared using pin-on-disk experiments in high vacuum and using an accelerated tape tester in ambient air. It was found that PFPE lubricants were mainly degraded by tribochemical reaction and mechanical shear. The durability of Z-TETRAOL and A20H are higher than conventional PFPE lubricant and lubricant on experimental tape. By using ultraviolet light treatment and by applying a stearic acid overcoat, the durability of PFPE lubricants could be improved.     

Dynamic tape path alternation with novel rotary guider

To enable higher recording density and data access accuracy, controlling lateral tape motion within high precision specifications through calibrated tape tension control is one of many key focuses for extra high density magnetic tape drives. This paper presents a novel rotary actuation mechatronic system which regulates travelling tape tension in a modern tape drive by dynamically alternating its tape path through closed-loop controls. Effectiveness of the system was demonstrated through calibrated laboratory parametric studies from which variation of travelling tape tension was found to be significantly reduced. The work described herein suggests engineering feasibility of using flangeless guiders in modern advanced tape drives as well as tape tension control without regulating tape drive??s driving motors.     

Control and operation of reel-to-reel tape drives without tension transducer

This paper presents the control and operation of reel-to-reel tape drives without any tension transducer. First, the tape drive model is validated while operating in the read/write or the velocity mode. Utilizing the coupled nature of the velocity-tension loop and the fact that the system is completely observable, the tension errors are estimated based on the validated model using state estimation techniques. The tension error estimates do not correlate well with the actual tension errors primarily due to the periodic disturbances caused by reel eccentricities during steady running and are not used for feedback purposes. In this paper, the controller design for such transports for the velocity and the position loops are presented. Due to lack of forced air in the tape path in such drives, there is considerable stiction/friction during start-up when the position loop is used. Feed forward currents which are functions of desired tension at the head and tape velocity are used for proper friction compensation. For systems using two tachometers, one for each reel, a linear velocity difference technique is presented which shuts down the drive in case of excessive or low tape tension and thus preserves tape integrity. Finally, test results are presented to illustrate the effectiveness of the design techniques.Paper presented at the 13th Annual Symposium on Information Storage and Processing Systems, Santa Clara, CA, USA, 17–18 June, 2002     

Study of durability and lateral tape motion of magnetic tape data storage media under high-speed operating conditions using magnetic and edge probe methods

The demand for large scale and efficient data storage systems has increased greatly over the past decade. The data storage industry has responded by increasing the capacity and cost-effectiveness of their systems. Magnetic data tape storage has similarly improved, with commercially available cartridges able to hold over 1.3 TB of compressed data on a single 3.5 in. form factor cartridge. These advancements are the results of a combination of several factors, which include both thinner tapes to improve volumetric density, and taking advantage of the improved magnetic coercivity of advanced magnetic coatings. As the storage capacity of magnetic tape systems continues to increase so does the need for faster read and write access. One possible way to achieve this is to translate the magnetic media past the read/write head at a higher velocity. This increased speed can have unwanted effects on the operation of the tape drive and media. This paper details a study of the effects that high-speed operation at different tensions can have on the performance of the system. The coefficient of friction between the tape and head was monitored to gauge durability and wear, and lateral tape motion (LTM) was monitored using both magnetic and edge probe methods to measure undesirable tape motion. Results for five different types of tape operating at five different tension/speed combinations are discussed in order to better determine the effects that tape characteristics and operating parameters have in high speed situations.     

基于蛇型磁带的海量数据排序算法

在数字图书馆和数据仓库中,需要解决海量数据的排序问题.利用蛇型磁带自身的物理特点,实现了一种高效的磁带排序算法STESort(serpentine tape external sort).与传统的2路归并磁带排序算法相比,STESort算法减少了磁带总定位时间.STESort算法具有更优的效率.STESort算法在提高排序效率的同时,通过减少磁头在磁带表面的移动次数延长了磁带的使用寿命.理论分析和实验结果表明,STESort算法优于传统的磁带排序算法,适合于海量数据排序.     

Quantitative study of magnetic tape abrasivity using accelerated wear testing

This paper presents a constant-area abrasion test (CAAT) method for the study of magnetic tape abrasivity over various operating conditions. The CAAT achieves its key features by employing an Alfesil (Al–Fe–Si) wear bar with a narrow, contoured bearing surface, and measuring very small amounts of wear by determining the reduction in cross-section of micro-indentations on the tape/wear bar contact surface. The combination of high-resolution wear measurements and a relatively small tape/wear bar contact area permit accelerated wear testing for tape abrasivity characterization. Effects of number of tape passes, tape tension, tape speed, temperature, and relative humidity on tape abrasivity were studied. Comparisons were made between the constant-area abrasion test (CAAT) and the conventional square-bar abrasion test (SBAT). The results of this study can be used to more accurately characterize coating and burnishing processes for producing magnetic tapes with proper abrasivity.     

Magnetic tape utilization viewed as an inventory control problem

Magnetic tapes are extensively used to store information. However, their low cost leads to problems in the efficient use of them as a storage media. There exists no scientific method to control the space utilization and the addition of new tapes to a tape library. A method is developed which provides control on the use of tapes, reduces the number of tapes in the library and minimizes the cost of storing information tapes.An inventory model is developed with the unused space on tapes as inventory. Replenishment can be done in one of two steps. The first deletes the expired datasets from the tapes and if the new inventory levels is less than S′, the least order level, a second step adds new tapes tapes to the library bringing the level up to S, the maximum order level. The level of inventory after replenishment can be anywhere between S′ and S′. The inventory model determines (1) When to delete expired datasets. (2) When to add new tapes to the library.No analytical solution is developed for the general cost equation for this model. However, an iterative procedure is offered which can be used to minimize the total cost of having unused space in the tape library.     

磁带节目管理系统的设计与实现

磁带和节目信息是广播电视机构媒体资产的重要内容。介绍了一个面向广电行业的磁带节目管理系统的具体设计和实现,该系统基于J2EE平台开发,采用IBM DB2数据库,整合了Struts和Hibernate框架,能够实现对磁带和节目信息的综合管理和高效查询,为广电行业信息化建设提供了良好的平台。     

Non-contact tape tension measurement and correlation of lateral tape motion and tape tension transients

Non-contact tension measurement of magnetic tape is performed. Light from a focussed light source is directed at a tape surface and the light reflected from the tape is captured by a photo cell. As the tape tension varies, the divergence of the reflected light bundle changes, i.e., the amount of light seen by the photo cell is a measure for the tension in the tape. Using this non-contact tension measurement approach and a high frequency lateral tape motion sensor, we have investigated the correlation between high frequency tension changes and high frequency lateral tape motion. Strong correlation is observed between the absolute values of tension and lateral tape motion.     

High frequency lateral tape motion and the dynamics of tape edge contact

Lateral motion of magnetic tape is investigated on roller and porous air-bearing type tape drives. The lateral tape motion signal is high-pass filtered and the spectral components are analyzed. Time-frequency analysis is also performed. The effect of dynamic tension changes during high frequency lateral motion events is examined, and the tension difference across the tape head is found to be correlated to the lateral motion of tape near the head. The effect of lateral motion of tape on tape pack winding is investigated and the frequencies observed during edge contact are analyzed.     

Robust regulation and tracking system design for multivariable control of the tape transport mechanism

Tape mechanisms must be able to transport the tape with a constant velocity for achieving high rate of data transfer. In this paper, a multivariable model of tape transport mechanism including the take-up and supply reel servos for tape tension control and capstan servo for speed control is considered. To achieve desired performance, pole-placement approach based on general canonical control form (GCCF) is used. Instead of using expensive tension sensors, an observer is designed. A regulator system is developed for disturbance rejection; and a modified integral control is designed for perfect tracking of desired set-points in tape speed and tensions. Since the real dynamic model associates with parametric uncertainties, an algorithm is developed for robust pole-placement. Eigenvalues of the uncertain control system are chosen such that appropriate responses are achieved while control efforts remain small bounded. Results show that robust performance is obtained for uncertain models with various parametric uncertainties.     

Study of magnitude and component frequency variation of lateral tape motion across an unsupported tape region

Magnetic data tape is one of the most cost-effective means of large scale information storage, and has the capacity to remain so in the future. Many challenges must be met in order to improve the storage density of magnetic tape systems and keep up with customer demands. One of these challenges is to minimize the relative motion between the read/write elements in the tape drive and the data tracks on the tape, also known as lateral tape motion (LTM). Modern closed-loop servo-based track following techniques are able to compensate for a large portion of the LTM events experienced, but care must still be taken in design of both the tape drive and tape media in order to minimize the negative effects of LTM. This paper details a study in which a new delay-integration method is applied to LTM measurement. The advantages and disadvantages of the method are discussed, and a comparison is made with previous LTM measurement methods. The delay-integration method is then applied to measure the change in LTM amplitude along an unsupported region of tape for several different tape samples. As many tape systems place the read/write head in the center of an unguided region, information about the behavior of tape in this situation could be used to minimize LTM, allowing for smaller data tracks and increased storage density.     

A method for fast tape backups and restores

This paper describes a method for fast backups and restores on tape drives. By using a tight synchronization between disk and tape accesses, the total throughput can be accelerated by a factor ranging from 30 to 100 per cent. The method imposes no special requirements on an operating system; only a timer with a resolution better than one fiftieth of a second is needed. Further, it can be used with virtually all types of streaming tapes and backup data formats.     

Photoacoustic determination of tension in magnetic tape

A non-contact method, using photoacoustically generated antisymmetric Lamb waves detected with a laser Doppler technique, is used for determining tension in magnetic tape. For the tape samples used in this study, the bending stiffness contributes as much to the overall stiffness as a 1 Newton tension force, so an accurate determination of the tension must also necessarily include an independent measurement of the bending stiffness. Our data shows that the flexural velocity normal to the direction of the applied tension provides a determination of the bending stiffness independent of tension. The dependence of the wavespeed on tension is measured, showing the expected tension dependence and demonstrating the utility of this approach.     

Polymerase chain reaction compatibility of adhesive transfer tape based microfluidic platforms

Laser patterned adhesive transfer tapes are a rapid, versatile, and low cost option to fabricate microfluidic platforms. In this work, we examined the compatibility with polymerase chain reaction (PCR) of different types of adhesive tape materials patterned with a CO₂ laser cutter. Acrylic, polyimide, and silicone-based tapes were considered. We performed a systematic study on off-the-shelf adhesive tapes with respect to fluid handling, PCR inhibition, reagent loss, and on-chip PCR reaction. A novel microfluidic PCR approach was implemented that combines the advantages of previously reported systems. It uses a thermal gradient from a single heating element and the thermocycling was carried out by passing the reaction mixture back and forth in a microfluidic channel strategically placed along the thermal gradient. Only the silicone-based tapes were compatible with on-chip PCR. The overall fabrication process takes less than 30 min, uses only off-the-shelf finished or semi-finished materials, and is amenable to large-scale reel-to-reel processing.     

Tape edge wear and its relationship to lateral tape motion

The relationship between tape edge wear and lateral tape displacement is investigated for a typical 12.7 mm (1/2 inch) tape drive. Tape edge wear is measured using atomic force microscopy, while lateral tape displacement is measured using an optical edge sensor. The lateral displacement signal is high-pass and band-pass filtered to examine the effect of tape edge wear on the dynamics of lateral tape displacement. In addition, time frequency analysis of the lateral displacement signal is performed.