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Storage Systems and HDD Technologies

FSTJ 2006-1 Cover Image

2006-1 (Vol.42, No.1)

In this special issue, we focus on the storage system technologies as applied to the long-term information storage and retrieval. We also describe Fujitsu's breakthrough technologies for HDDs, which are the core storage system elements for achieving further increases in recording density.
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2006-1 (Vol.42, No.1) Contents

1. Preface (21 KB)
In terms of storage capacity, the worldwide storage market is expanding by 70% per year. This rapid increase is mainly due to the strong growth of IT applications such as banking transactions, electronic documentation, and shopping at online music stores, which require more storage capacity than the applications of traditional large enterprise systems. ---[Chiaki Ito, Corporate Executive Vice President]

Part 1 Storage Systems

2. Technologies of ETERNUS6000 and ETERNUS3000 Mission-Critical Disk Arrays (106 KB)
Fujitsu has developed the ETERNUS6000 and ETERNUS3000 disk arrays for mid-range and high-end IT market segments. These segments have been growing because IT systems have shifted from server-centric data processing architectures to information-centric architectures. This paper introduces the system architecture; high-reliability, high-performance, and high-availability features; and technologies of the ETERNUS6000/3000. Section 2 describes the controller modules, channel adapters, device adapters, routers, and device enclosure features. Section 3 describes the high-reliability features such as cyclic mirroring, block check codes, DB Guard, and redundant copying. Section 4 describes the high-availability RAID migration and logical device expansion features. Lastly, Section 5 describes the high-performance technologies of these RAID subsystems. ---[Yoshinori Terao]
3. Remote Copy Technology of ETERNUS6000 and ETERNUS3000 Disk Arrays (90 KB)
This paper gives an overview of a storage-system remote copy function and the implementation of such a function in Fujitsu's ETERNUS3000 and ETERNUS6000 disk arrays. Recently, disaster recovery features have become important for mission-critical systems. A storage-system remote copy function is often used by high-end disaster recovery systems. The ETERNUS3000 and ETERNUS6000 series both have a remote copy function called Remote Equivalent Copy (REC). The ETERNUS6000 series REC operates in both synchronous and asynchronous mode. The ETERNUS3000 series REC operates only in synchronous mode. Both RECs provide the performance and functionalities required to construct various kinds of disaster recovery systems. ---[Tsutomu Akasaka]
4. Technologies of ETERNUS VS900 Storage Virtualization Switch (253 KB)
This paper gives an outline of storage virtualization and then describes a new-generation storage virtualization system that is based on Fujitsu's ETERNUS VS900 storage virtualization switch. The VS900 provides a simplified, logical view of a complicated storage system and simplifies storage management. It adopts a network-based, out-of-band virtualization model. Among other advantages, the VS900 provides high performance, reliability, and availability. It is managed by Systemwalker Resource Coordinator, which not only manages a storage system but also manages other system resources such as servers and networks to enable unified system-wide management. ---[Takeshi Ito, Atsuo Ouchi]
5. Technologies for Realizing New ETERNUS LT270 High-End Tape Library System (315 KB)
The future of magnetic tape as the external memory device of computer systems was once questioned when it lost ground to the optical disk and other devices. However, magnetic tape is regaining popularity because its fast transfer rate and low cost make it suitable for use in fast, large-capacity storage systems. Such systems are in especially high demand for use as backup systems that protect against disasters, but they are also increasingly being used for archival storage. In addition to the requirements of large capacity and high speed, scalability to meet the growth of users' systems is especially important for open systems that handle large amounts of multimedia information. Also important are high reliability, high availability, and continuous operation. Fujitsu has developed a new magnetic tape library called the ETERNUS LT270 that meets today's requirements such as large capacity and high reliability, expandability, and availability. This paper outlines the features and technologies of the ETERNUS LT270. ---[Yasuhiko Hanaoka, Makoto Sasaki, Akira Takano]
6. Technologies of ETERNUS VT600 Virtual Tape System (195 KB)
Faster tape processing and a lower total cost of ownership (TCO) are required for IT applications that use a magnetic tape system. The ETERNUS VT600 virtual tape system was developed to meet these needs. It achieves major improvements in speed, reliability, and functionality by combining an innovative tape virtualization technology with the latest Storage Area Network (SAN) technologies and hardware components. This paper introduces the architecture, functions, and advantages of the ETERNUS VT600. ---[Takashi Miyako, Tatsuya Ohmido]
7. Technologies of ETERNUS Virtual Disk Library (130 KB)
In today's dramatically changing business environment, the extensive broadband environment and digitization of information enable huge amounts of information to be distributed over a network. The volume of fixed content such as multimedia data and intra-company data such as e-mail archives is rapidly increasing. Because the value of this data changes over time, the most suitable storage system for the value should be selected. The ETERNUS Virtual Disk Library answers this need by autonomously controlling data according to its value and reduces not only the hardware cost of a storage system but also the operational data management cost. This paper outlines the ETERNUS VD800 virtual disk controller and describes how it performs autonomous data control in the ETERNUS Virtual Disk Library. ---[Shigeo Konno, Tadashi Kumasawa]
8. Archive Storage Technologies Supporting Information Lifecycle Management (134 KB)
A large amount of fixed content has been generated due to the ongoing development of the broadband Internet and digital information technology. Moreover, the information contained in e-mails and system logs, and other information must be securely preserved for a certain period, though not yet legally mandated by such legislation as the Sarbanes-Oxley Act and SEC Rule 17a. Consequently, there is a growing need for a special archive storage system that efficiently preserves and manages a large amount of content at low cost. Fujitsu has taken the lead in addressing this need by combining a high-speed disk array device with a low-cost tape library device for the first time, and developed ETERNUS3000 Archive Storage. This paper describes the problems posed by saving fixed content data, and explains the functions and use of ETERNUS3000 Archive Storage that efficiently manages and enables a longer preservation lifecycle for fixed content. ---[Noboru Osada, Kunihiko Kassai]
9. High-Speed Backups without Stopping Business Applications (82 KB)
The growing demand for 24 × 7 system operations has increased the demands for technologies that back up business volumes online without needing to stop the business applications. Fujitsu provides high-speed backup and recovery solutions for SQL Server, Exchange, Oracle, and DB2 databases. These solutions simplify and reduce the cost of Oracle database backups and recoveries. This paper introduces several techniques for making backups without needing to stop the business applications. It also describes ways to simplify and reduce the cost of system operations. ---[Isao Igarashi]

Part 2 HDD

Hard Disk Drive Technologies

10. Trends in Enterprise Hard Disk Drives (139 KB)
The storage capacity and performance of Enterprise HDDs have been steadily enhanced in the past, but now HDD development has reached a turning point. For the 3.5-inch HDD, 300-GB capacity has been achieved for 10 000-rpm drives to satisfy storage requirements. Now, there is a shift towards 15 000-rpm drives in pursuit of higher performance. Moreover, to address the requirements for compactness, power saving, and higher performance through the use of multiple spindles, 2.5-inch HDDs are now commercially available. Regarding Small Computer System Interface (SCSI), the limits of transfer speed have been reached, resulting in a switch towards Serial Attached SCSI (SAS) that employs high-speed serial transmission technology. In response to these market changes, Fujitsu has added a range of AL-9SE 2.5-inch HDDs to its AL-9 series and assumed the industry lead by supporting SAS (3 Gb/s). This paper summarizes trends in the general market and technologies for enterprise HDDs, and gives an overview of the features and technologies of the AL-9 series; Fujitsu's latest series of HDDs designed to cater to current market needs. ---[Seiichi Sugaya]
11. Mobile HDDs (127 KB)
Fujitsu has developed 120 GB and 160 GB capacity HDDs for notebook PCs and other mobile applications. The high capacities of these drives open up new market opportunities such as mobile audio-video applications. This paper introduces Fujitsu's MHV series of mobile HDDs, which are our latest 2.5-inch models. The MHV series feature an areal density of 99.1 Gbit/in2, which is the world's highest for a 2.5-inch drive. Also, they have a 150 MB/s transfer speed serial-ATA (SATA) interface with Native Command Queuing (NCQ), are very rugged and quiet, and are very popular with our customers. This paper introduces the head, medium, mechanical, and electronic technologies of the MHV series. ---[Shigenori Yanagi]
12. HDD Interface Technologies (108 KB)
The interfaces of hard disk drives (HDDs) have been changed to serial interfaces to meet the demands for high-speed data transfer. The main interfaces involved are the Fibre Channel (FC), Serial ATA (SATA), and Serial Attached SCSI (SAS). Up to now, the HDD market segments corresponded to the serial interfaces that were available. Because of the recent demands for cost reduction, however, requests are being made for serial interfaces optimized for the use of the HDD units. As a result, the HDD market segments have become fractionalized, and the correspondence between the market segments and serial interfaces has also been lost. For example, products in which a conventional low-end SATA and a large-capacity HDD are combined have begun to appear on the market as enterprise HDDs. This paper describes the features of these serial interfaces and the interface technologies of the HDD controller that enables serialization of the interfaces. It also discusses the technological problems of future HDD interfaces and their solutions. ---[Masakazu Kawamoto]

Advanced Mechanical and Measurement Technologies

13. Servo Track Writing Technology (197 KB)
To increase the recording density of hard disk drives (HDDs), it is indispensable to improve the servo track writing (STW) technology that writes the servo positioning information used to position the magnetic recording head onto the data track. Previously, it was popular to write the servo tracks by using the HDD's own head and positioning it using an external actuator. Recently, however, the demand for higher productivity and STW quality has been growing, and a new method is needed. As a manufacturer of HDDs, Fujitsu is developing various STW technologies to meet this need. This paper introduces the major STW methods and requirements for STW and then describes the factors that reduce STW quality. Then, it describes media STW and magnetic printing STW, which are typical external writing methods. ---[Tomoyoshi Yamada, Masanori Fukushi, Hiroyuki Suzuki, Kazuhiko Takaishi]
14. Nano-Scale Simulation Technologies (251 KB)
Physical simulation technologies are employed in various areas of HDD development and design. These include structural analysis (vibration, impact shock), thermal fluid analysis (thermal deformation, heat dissipation), fluid analysis (head flight, airflow within a drive, contamination behavior), magnetic field analysis (read heads, write heads, motors), electromagnetic field analysis (signal transmission, EMI, immunity), and manufacturing process analysis (plating, ion milling, deposition). Thermal fluid analysis and manufacturing process analysis require nano-order precision to further increase HDD recording density. To meet this requirement, Fujitsu has developed and is actively using simulation techniques for analyzing head element protrusion and the ion milling and deposition processes. This paper focuses on the analysis of head element protrusion to minimize head flying height and the analysis of ion milling and deposition processes to further reduce the size of head element structures, with the overall aim of further increasing HDD recording density. ---[Toshiyuki Nakada, Kenichiro Aoki, Atsushi Furuya]
15. Head Disk Interface Technologies for High Recording Density and Reliability (131 KB)
Various technologies are being developed to simultaneously achieve a high-density storage capacity and high-reliability in hard disk drives. Some examples are technologies for reducing the gap between the head and magnetic layer of the disk while providing an accurate grasp of the conditions at the nano level and technologies for controlling the head's flying height at the nano level. Fujitsu is developing these technologies to improve the storage density and reliability of hard disk drives. In this paper, we describe the following Head Disk Interface technologies: a Co-Axial Impact Collision Ion Scattering Spectroscopy technique for evaluating the coverage properties of lubricants, technique for evaluating the coverage properties of the overcoats used on magnetic storage devices based on the Drop method, and a chemical treatment technology for the flying surface of the head slider. ---[Yasuyuki Goto, Norikazu Nakamura, Akiyo Mizutani, Hiroshi Chiba, Keiji Watanabe]

Advanced Magnetic Recording Technologies

16. Ultra High Density Perpendicular Magnetic Recording Technologies (234 KB)
Perpendicular magnetic recording (PMR) has been investigated for ultra high density magnetic recording since 1977. The main problems affecting PMR are wide area data erasure, deterioration of the bit error rate (BER) due to noise from the soft magnetic underlayer (SUL), and the high media production cost of a thick SUL to secure an adequate BER at high recording densities. To overcome these problems, we have developed a media and head that use new technologies. These technologies are a double recording layer with a granular recording layer, an anti-parallel structure (APS)-SUL, and a trailing shielded head. These technologies improve the performance of PMR to over 200 Gbit/in2, which is sufficient for practical use. This paper describes these media and head technologies and an investigation of signal processing for PMR channels that compares partial response (PR) targets containing a DC response. ---[Isatake Kaitsu, Ryosaku Inamura, Junzo Toda, Toshihiko Morita]
17. Advanced Technologies in Synthetic Ferrimagnetic Media (136 KB)
Recently, synthetic ferrimagnetic media (SFM) have been widely employed as high-density recording media for hard disk drives (HDDs). The signal-to-noise ratio (SNR) and thermal stability of magnetically written bits have been improved by three new SFM technologies. The first technology greatly improves the SNR in the lower areal magnetization region by increasing the magnetic anisotropy energy of the stabilizing layer without degrading the thermal stability. The second is an exchange enhancement technology that uses a Co-based layer adjacent to the Ru exchange coupling layer to improve the thermal stability without degrading the SNR. On SFM media that incorporate this second technology, stable, non-percolating high-density patterns of up to 900 kfci were clearly observed using high-resolution magnetic force microscopy (MFM). The third technology uses a separated recording layer with a Ru/CoCr/Ru exchange-coupling layer (separated-SFM) to provide a more than 50% reduction of medium noise power with the same or better thermal stability than that of conventional SFM. These technologies enable the design of practical media for recording densities over 150 Gbit/in2. This paper introduces these new SFM technologies. ---[Iwao Okamoto]
18. TMR Film and Head Technologies (179 KB)
We have developed Al-O barrier magnetic tunnel junctions (MTJs) and obtained a magneto-resistance (MR) ratio of 27% with a resistance-area product RA of about 3 Ωμm2. We have also studied Ti-O and Mg-O as new low barrier energy materials for MTJs. Ti-O barrier MTJs showed a very small RA of less than 2 Ωμm2. We can obtain a high MR ratio of about 100% for Mg-O barrier MTJs with an RA of 2 to 3 Ωμm2 using a CoFeB magnetic layer for the pinned and free layers. The coercivity of the free layer can be reduced using a Co74Fe26/NiFe free layer, which is suitable for head applications. An MR ratio of 40 to 50% was obtained with an RA of 2 to 3 Ωμm2. Mg-O barrier MTJs are the most promising for future TMR heads for recording densities over 200 Gbit/in2. We fabricated Al-O barrier TMR heads whose target areal recording density is around 100 Gbit/in2. These heads have a 25% MR ratio with an RA of 4 Ωμm2, and the width and height of the TMR head element are 110 nm and 100 nm, respectively. We can obtain an average output signal of about 5000 μVpp at a 150 mV bias voltage (Vb) using a synthetic ferrimagnetic medium. We have also investigated the characteristics of head noise and found that thermal magnetic noise is the dominant noise in our TMR heads. We also investigated the thermal magnetic noise as a function of the exchange coupling field Hex between the pinned and antiferromagnetic layers of TMR heads by using micromagnetic simulations. We clarified the importance of increasing not only the MR ratio but also Hex to realize ultra high density magnetic recording. ---[Kazuo Kobayashi, Hideyuki Akimoto]

Technologies for Terabit Recording

19. CPP-GMR Technology for Future High-Density Magnetic Recording (126 KB)
To realize a Current-Perpendicular-to-Plane Giant Magnetoresistance (CPP-GMR) magnetic read head, we have enhanced the CPP magnetoresistance of fully metallic spin-valves by developing two groups of new magnetic materials for each magnetic layer. The first group are spin-blocking materials that control the spin-dependent transport through the synthetic ferrimagnet pinned layer using impurities. Pinned layers of these new materials do not have the low magnetoresistance disadvantage of the synthetic pinned layer in CPP spin-valves. The other group are high-resistivity magnetoresistive materials that contain a relatively high resistivity metal and have spin-dependent scatterings. These materials expand the possibility of improving the output of the CPP-GMR, which has a small resistance, and enable recording densities in excess of 300 Gbit/in2. Because a high output, high signal-to-noise ratio, and low resistance are required in read sensors for high-density recording and fast data-transfer, CPP-GMR technology will be indispensable for the future system of high-density magnetic recording. ---[Keiichi Nagasaka, Arata Jogo, Takahiro Ibusuki, Hirotaka Oshima, Yutaka Shimizu, Takuya Uzumaki]
20. Thermally Assisted Magnetic Recording (142 KB)
Thermally assisted magnetic recording can solve fundamental problems concerning thermal fluctuation and write capability in magnetic recording, and it is regarded as the key technology for achieving densities exceeding 1 Tbit/in2. This technology is classified into optical dominant recording and magnetic dominant recording. This paper describes these two methods and the differences between them. A theoretical estimation in optical dominant recording suggests that thermally assisted magnetic recording enables 10 times the density compared with conventional magnetic recording. Magnetic dominant recording was conducted on longitudinal synthetic ferrimagnetic recording media to prove its fundamental effectiveness. The signal-to-noise ratio and overwritability of thermally assisted magnetic recording without thermal erasure were assured. A newly proposed optical head with a butted grating structure provides good optical characteristics as the heating element for optical dominant recording, and its fabrication process is compatible with the process for the conventional magnetic head. This paper also describes the results of experimental thermally assisted magnetic recording and the fundamental design of a heating element that uses near field optics. ---[Koji Matsumoto, Akihiro Inomata, Shin-ya Hasegawa]

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