CHAPTER 2 DATA BUFFER MANAGEMENT

2.1Data Buffer

2.2Look-Ahead Cache Feature

2.3Write Cache

In this chapter, the configuration of the data buffer with which the IDD is equipped, its operation and the operation of the cache feature are described.

2.1Data Buffer

2.1.1Data buffer configuration and basic operation

The IDD is equipped with a data buffer, which makes it possible to efficiently execute data transfer operations between INIT (initiator) and a disk drive. The IDD have a 7,864 KB data buffer.

The data buffer, the IDD divided into 256 cache pages and can be assumed the cache segment by uniting two or more pages. Dividing of the data buffer is controlled by the MODE SELECT parameter (cache segment parameter: Page code = 8).

Each data buffer is 2 ports of FIFO (First-In First-Out) ring buffer, with one port allocated for transfers with the disk media and the other port for data transfers with the SCSI bus. Mutual ports operate asynchronously and since it is possible to efficiently absorb variations in data transfer speed between the ports, the INIT can perform data transfer operations with the IDD while being virtually unaware of differences between the SCSI bus data transfer rate and the disk drive data transfer rate.

Even if the data transfer capacity of the SCSI bus (INIT) is lower than the disk drive's data transfer rate, the data buffer can perform data transfers to the system under optimum conditions without using sector interleave. Also, if the data transfer capacity of the SCSI bus (INIT) is higher than the disk drive's data transfer rate, it is possible to minimize the occupancy time on the SCSI bus by accumulating an appropriate amount of data in the data buffer.

Only one cache segment by uniting two or more pages of the divided data buffer is used by one command and the data in the other cache segments are held.

Figure 2.1 shows the data buffer image.

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Fujitsu MAN3184, MAN3367, MAN3735 SERIES DISK DRIVES specifications Data Buffer Look-Ahead Cache Feature Write Cache
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MAN3735, MAN3184, MAN3367, MAN3735 SERIES DISK DRIVES, MAN3367, MAN3184 specifications

Fujitsu's MAN3184, MAN3367, and MAN3735 series disk drives represent a significant advancement in storage technology, catering to the needs of businesses seeking reliability, performance, and high capacity. These drives are designed for enterprise environments, providing exceptional data integrity and speed essential for effective data management.

The MAN3184 series is renowned for its high rotational speed of 10,000 RPM, which significantly enhances data access times. With a capacity of up to 18.4 GB, these drives are suitable for applications requiring quick read and write operations. The series employs an improved read/write head technology, which reduces latency and increases overall performance. This technology is complemented by advanced error correction mechanisms, ensuring the reliability necessary for critical data applications.

Transitioning to the MAN3367 series, these drives offer increased storage capacity and improved performance metrics. With capacities reaching up to 36.7 GB, they cater to growing data demands in modern enterprises. They also feature a 10,000 RPM spindle speed, ensuring that the drives can handle intensive workloads with ease. The MAN3367 drives include SCSI interface support, making them versatile and easy to integrate into various systems. The inclusion of intelligent caching algorithms allows for faster data retrieval, while built-in thermal management features ensure optimal performance, even under heavy usage.

The MAN3735 series takes performance up another notch, boasting higher capacities of up to 73.5 GB. These drives are particularly suited for environments that require high reliability and availability. The series utilizes a state-of-the-art SCSI Ultra160 interface, which maximizes data transfer rates, ultimately enhancing overall system efficiency. Additionally, the MAN3735 series employs advanced data protection technologies, including power loss protection and predictive failure analysis, which proactively minimizes potential downtime.

All these series of Fujitsu disk drives are built with a focus on durability and sustained performance. They are designed to operate seamlessly in high-demand environments, ensuring that organizations can rely on them for critical applications. Their compact design and energy-efficient operation make them an ideal choice for modern data centers looking to optimize space and reduce power consumption.

In summary, Fujitsu's MAN3184, MAN3367, and MAN3735 series disk drives deliver a blend of high capacity, performance, and reliability. These drives incorporate advanced technologies that address the evolving needs of enterprise storage solutions, making them a valuable asset for any organization aiming to enhance their data management capabilities.
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