Toshihiro Uehara

Study of Integrated Services with broadcasting, stored and Internet contents

This paper presents a method for realizing Integrated Services with broadcasting, stored and Internet contents, on the Broadcasting System Based on Home Servers by using metadata. The set of metadata needed for the services and the method of integrated showing using metadata are described.

A high-availability software update method for distributed storage systems

SUMMARY In this paper, we propose a nonstop system upgrademethod without significant performance degradation fordata management software. To reduce disk accesses andnetwork traffic, we construct logical nodes inside a physicalnode and migrate data between the symbiotic logical nodes.This logical migration is assisted by storage managementfunctions that hide data location and migration from users.We also show the effectiveness of our method using experi-mental results on the system based on the AutonomousDisks we have proposed as a highly available storage sys-tem technology.

A new 8-14 channel coding for D-3 format VTR

An 8-14 channel coding method suitable for high density recording for digital VTRs was developed. Using this coding, an 8-b data word is transformed into 14-b code word, assuming that the distance between magnetic polarity transitions is two to seven channel bits, the maximum absolute of the DSV (digital sum variation) is seven. The code has a minimum recorded wavelength 14% longer and a required bandwidth 12.5% narrower than those of S-NRZ and M/sup 2/ codes. Since it is a run-length-limited block code, it provides simplified recording and reproduction equalization, azimuth and overwrite recording, no error propagation to any other word, and error detection. The signals encoded by applying this method as well as S-NRZ and M/sup 2/ to 64-Mb/s M-sequence data were recorded and reproduced using metal particle tape and a Sendust laminated sputtered type head. The results show that the reproduced SNR of 8-14 channel coding was 2.8 dB higher than those of S-NRZ and M/sup 2/. >

Investigation of particulate media with an ultra-thin magnetic layer suitable for MR heads on a rotating drum

To improve recording density and data transfer rate, we investigated the electromagnetic characteristics of the combination of the MP with an ultra-thin magnetic layer (U-MP) and MR head on a rotating drum. The magnetic layer thickness was reduced to 40-90 nm, and the magnetic particles volume was one-third of conventional ones. Reproduced output of the U-MP/MR combination was at least ten times higher than that of the combination of a conventional MP and MIG head. The areal recording density was estimated to be 6 times as large as that of the conventional MP/MIG combination.

New 8-14 channel coding for high-density recording

The D-3 has achieved a recorded density some 2.5 times higher than those of conventional VTRs. Channel coding, which is capable of high-density recording and is suited for the head-tape recording system, is one of todays most important high-density recording technologies, and a new 8-14 channel coding has been developed and employed for the D-3 format. The paper presents the requirements for channel coding which are required in digital VTRs and explain in detail the generation of the new 8-14 channel coding meeting these requirements, which is a type of DC-free run-length-limited block coding. It explains the actual procedure and configurations of the channel encoder/decoder for 8-14 channel coding. It also compares and examines channel coding methods that have been used until now from several aspects, and describes their features.< >

An Efficient Access Forwarding Method Based On Caches On Storage Nodes

In this paper, we discuss access forwarding schemes for the replication that achieve balanced access load distribution for data replicas on multiple storage nodes. In parallel storage systems, it is significant to handle skew of accessrequest distribution. Although replication is commonly used to solve such problems, it decreases hit ratios of cache memories on each storage nodes. We first obtain a result that it uses cache memories efficiently to forward accesses that target at data in less demand with a simple experiment. We also propose a method that uses hit ratios of each cache to recognize the popularity of data with low costs. Results of experiments with the method show that it helps the replication use the limited cache space efficiently.

The Versioning System Balancing Data Amount and Access Frequency on Distributed Storage System

In this paper, a method of balancing both access frequency and data amount for a distributed parallel storage system under version management is discussed. We assume the version management method keeps the latest version of file and a number of differential information sets to access previous versions. Since the access frequency for an aged version is tend to be lower than that for the latest version, we control the access frequency distribution by the placement of the latest versions, while the data amount distribution is managed by the placement of the differential information whose size is enough small to adjust the subtle difference of data amount. We propose a distributed directory structure and data placement algorithm, and evaluate its effect on the access frequency and data amount distribution.

Performance analysis of hierarchical storage management systems for video retrieval system

This paper presents new performance comparison parameters for hierarchical storage management systems (HSMS) for video retrieval systems. These parameters are average access time and average operating time. The overall performance of the two prototype systems with HSMS, one with an optical disk and HDD and the other with magnetic tape and HDD, are described.

High-density reproduction characteristics with MR head for rotary drum in helical-scan tape system

A magneto-resistive (MR) head for a rotary drum in a helical-scan tape system has been developed to realize a high-capacity tape storage system with a high data transfer rate that uses a small cassette. Also, various experimental ME (Metal Evaporated) tapes whose magnetic layer thickness is 0.1 /spl mu/m or less (thin-magnetic-layer ME tapes) for the MR head has been fabricated. Reproduction characteristics of the MR head with the ME tapes was evaluated. The output voltage of the MR head was 20 times that of a conventional inductive head. An areal recording density of 1.2 Gbit/inch/sup 2/ was found to be possible combining the MR head with the thin-magnetic-layer ME tapes whose magnetic layer thickness was 0.09 /spl mu/m.

High-Density Reproduction Characteristics of an MR Head for a Rotary Drum in a Helical-Scan Tape System.

We have evaluated the reproduction characteristics of a magnetoresistive (MR) head for a rotary drum in a helical-scan tape system. This MR head was developed for use in a high-capacity tape storage system that has a high data transfer rate and uses a small cassette. Various experimental thin-magnetic-layer metal evaporated (ME) tapes suitable for the MR head, whose magnetic layer thickness is 0.1 μm or less, have been made, and our evaluation was done using such tapes. We found the output voltage of the MR head was 20 times that of an inductive head, and an areal recording density of 1.2 Gbit/ inch2 was feasible with the combination of the MR head and the thin-magnetic-layer ME tapes. Moreover, the pulse width and CN ratio showed that the optimum value of Brδ, the product of remanent flux density and magnetic layer thickness of the tape, for the trial MR head was from 140 to 220 G·μm.