If the number of write data logical blocks exceed the size of the segment being written into, when the end of the segment is reached, the data is written into the beginning of the same cache segment, overwriting the data that was written there at the beginning of the operation; however, the drive does not overwrite data that has not yet been written to the medium.

If write caching is enabled (WCE=1), then the drive may return Good status on a write command after the data has been transferred into the cache, but before the data has been written to the medium. If an error occurs while writing the data to the medium, and Good status has already been returned, a deferred error will be gen- erated.

The Synchronize Cache command may be used to force the drive to write all cached write data to the medium. Upon completion of a Synchronize Cache command, all data received from previous write commands will have been written to the medium.

Table 18 shows the mode default settings for the drive.

4.5.2Prefetch operation

If the Prefetch feature is enabled, data in contiguous logical blocks on the disc immediately beyond that which was requested by a Read command are retrieved and stored in the buffer for immediate transfer from the buffer to the host on subsequent Read commands that request those logical blocks (this is true even if cache operation is disabled). Though the prefetch operation uses the buffer as a cache, finding the requested data in the buffer is a prefetch hit, not a cache operation hit.

To enable Prefetch, use Mode Select page 08h, byte 12, bit 5 (Disable Read Ahead - DRA bit). DRA bit = 0 enables prefetch.

The drive does not use the Max Prefetch field (bytes 8 and 9) or the Prefetch Ceiling field (bytes 10 and 11).

When prefetch (read look-ahead) is enabled (enabled by DRA = 0), the drive enables prefetch of contiguous blocks from the disc when it senses that a prefetch hit will likely occur. The drive disables prefetch when it decides that a prefetch hit is not likely to occur.

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Cheetah 15K.5 FC Product Manual, Rev. D

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Seagate ST3146855FC, ST3300655FC, ST373455FC manual Prefetch operation
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ST3146855FC, ST373455FC, ST3300655FC specifications

Seagate is renowned for its commitment to high-performance data storage solutions, and their range of enterprise drives, including the ST3300655FC, ST373455FC, and ST3146855FC, demonstrates this dedication. These models cater to businesses requiring robust, reliable, and efficient hard disk drives (HDDs) designed for demanding environments.

The ST3300655FC offers a capacity of 300 GB, making it suitable for a variety of enterprise applications. It utilizes a 15,000 RPM spindle speed, which significantly enhances its performance, delivering quick read and write times. This drive supports Serial Attached SCSI (SAS) interface, ensuring faster data transfer rates and reliability essential for critical computing environments. The dual-port connectivity of SAS allows for enhanced fault tolerance and redundancy, making the ST3300655FC ideal for data centers and enterprise storage systems.

Following closely, the ST373455FC provides a slightly larger capacity of 734 GB while maintaining the same 15,000 RPM speed. This drive's design focuses on high availability, making it an excellent choice for applications that require continuous uptime. Like its counterpart, it also benefits from the SAS interface, ensuring that data can be accessed quickly and reliably. The robust construction of the ST373455FC guarantees consistent performance under heavy workloads, an essential characteristic for enterprise use.

The ST3146855FC, with a capacity of 146 GB, offers a balance between speed and storage for enterprises that do not require the larger capacities provided by the other two models. It also operates at 15,000 RPM, benefiting from similar technological advancements as the ST3300655FC and ST373455FC. This drive maintains compatibility with existing systems, making it a versatile option for organizations looking to upgrade their storage solutions without overhauling their infrastructure.

All three models exhibit Seagate's commitment to durability and low power consumption, which is critical for reducing operational costs in data centers. They also feature advanced error recovery and data integrity technologies, ensuring that critical data remains intact and accessible. Enhanced thermal and vibration tolerance further extends the lifespan of these drives in challenging environments.

In summary, the Seagate ST3300655FC, ST373455FC, and ST3146855FC are tailored to meet the rigorous demands of enterprise environments. Their high spindle speeds, SAS connectivity, and robust designs make them exemplary choices for businesses seeking reliable and efficient storage solutions. Their distinctive features and technologies ensure that they deliver outstanding performance, data integrity, and durability, making them invaluable assets in any data-driven organization.
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