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 IDD divides data buffer into 64 Pages, which are minimum allocation size for Cache. Actually two or more Pages are linked and a Cache Segment is constructed per the requested data size from INIT.

Since IDD automatically controls the best suitable Cache Segment, INIT cannot be changed neither the Page size nor the Segment size.

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 MAP3147, MAP3367, MAS3735, MAP3735, MAS3367 specifications Data Buffer Look-Ahead Cache Feature Write Cache
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MAP3735, MAP3147, MAS3367, MAP3367, MAS3735 specifications

Fujitsu, a renowned leader in technology and innovation, has developed a variety of reliable hard disk drives (HDDs) that cater to a wide range of data storage needs. Among these, the MAS3735, MAP3367, MAS3367, MAP3147, and MAP3735 series stand out for their advanced features and exceptional performance.

The MAS3735 is a high-capacity enterprise-class drive that boasts a storage capacity of up to 300 GB. Its 10,000 RPM spindle speed ensures rapid data retrieval and efficient performance, making it ideal for data-intensive applications. It utilizes a Serial Attach SCSI (SAS) interface, which allows for improved data transfer rates and increased reliability compared to traditional SATA drives. The drive is designed with advanced technologies such as error recovery and data integrity features, ensuring the safety and security of critical data.

Similarly, the MAP3367 and MAS3367 models are geared towards both enterprise and mid-range server environments, providing a storage capacity of up to 300 GB as well. These drives also operate at a spindle speed of 15,000 RPM, offering swift access times that enhance overall system performance. The MAP3367 employs the Ultra 320 SCSI interface, allowing for significant bandwidth and ensuring data is transmitted efficiently.

On the other hand, both MAP3147 and MAP3735 models provide versatile solutions for various applications, supporting capacities from 36 GB to 147 GB. The MAP3147, with its 10,000 RPM speed, is optimized for workloads requiring quick access and high throughput, making it suitable for transactional systems and enterprise applications. The MAP3735, while offering comparable capacity, emphasizes exceptional reliability and durability, which is crucial for environments that involve heavy data loads.

All these Fujitsu HDDs are characterized by their robust construction, reliability, and efficiency. They are built to withstand heavy workloads and are equipped with features like advanced thermal management and acoustic noise reduction, ensuring they operate effectively in data center environments.

In conclusion, Fujitsu's MAS3735, MAP3367, MAS3367, MAP3147, and MAP3735 series HDDs are designed for high performance and reliability, catering to both enterprise and mid-range environments. Their advanced features make them a strong choice for businesses looking to enhance their storage solutions while maintaining data integrity and system performance.
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