7.0Defect and error management

The drive, as delivered, complies with this product manual. The read error rates and specified storage capaci- ties are not dependent upon use of defect management routines by the host (initiator).

Defect and error management in the SCSI protocol involves the drive internal defect/error management and SAS system error considerations (errors in communications between the initiator and the drive). Tools for use in designing a defect/error management plan are briefly outlined in this section. References to other sections are provided when necessary.

7.1Drive internal defects/errors

During the initial drive format operation at the factory, media defects are identified, tagged as being unusable, and their locations recorded on the drive primary defects list (referred to as the “P’ list and also as the ETF defect list). At factory format time, these known defects are also reallocated, that is, reassigned to a new place on the medium and the location listed in the defects reallocation table. The “P” list is not altered after factory formatting. Locations of defects found and reallocated during error recovery procedures after drive shipment are listed in the “G” list (defects growth list). The “P” and “G” lists may be referenced by the initiator using the Read Defect Data command.

Details of the SCSI commands supported by the drive are described in the SAS Interface Manual. Also, more information on the drive Error Recovery philosophy is presented in the SAS Interface Manual.

7.2Drive error recovery procedures

When an error occurs during drive operation, the drive, if programmed to do so, performs error recovery proce- dures to attempt to recover the data. The error recovery procedures used depend on the options previously set in the Error Recovery Parameters mode page. Error recovery and defect management may involve using sev- eral SCSI commands described in the SAS Interface Manual. The drive implements selectable error recovery time limits required in video applications.

The error recovery scheme supported by the drive provides a way to control the total error recovery time for the entire command in addition to controlling the recovery level for a single LBA. The total amount of time spent in error recovery for a command can be limited using the Recovery Time Limit bytes in the Error Recovery mode page. The total amount of time spent in error recovery for a single LBA can be limited using the Read Retry Count or Write Retry Count bytes in the Error Recovery mode page.

The drive firmware error recovery algorithms consists of 11 levels for read recoveries and five levels for write. Each level may consist of multiple steps, where a step is defined as a recovery function involving a single re- read or re-write attempt. The maximum level used by the drive in LBA recovery is determined by the read and write retry counts.

Table 14 equates the read and write retry count with the maximum possible recovery time for read and write recovery of individual LBAs. The times given do not include time taken to perform reallocations. Reallocations are performed when the ARRE bit (for reads) or AWRE bit (for writes) is one, the RC bit is zero, and the recov- ery time limit for the command has not yet been met. Time needed to perform reallocation is not counted against the recovery time limit.

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Seagate ST936701SS, ST973401SS Defect and error management, Drive internal defects/errors, Drive error recovery procedures
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ST936701SS, ST973401SS specifications

The Seagate ST936701SS and ST973401SS are high-performance enterprise hard drives designed for optimal data storage solutions in demanding environments. Both models belong to Seagate's Savvio series, which is renowned for its reliability and efficiency. These drives are tailored for critical applications such as database management, data warehousing, and online transaction processing.

The ST936701SS comes with a storage capacity of 36.4 GB, while the ST973401SS offers a larger capacity of 73.4 GB. This variance allows users to choose the drive that best suits their storage needs without compromising performance. Both drives utilize a 2.5-inch form factor, making them compact and suitable for high-density storage configurations.

A key feature of these drives is their impressive rotational speed of 10,000 RPM, which enhances data access times and improves overall system responsiveness. This speed allows for reduced latency and faster data transfer rates, critical for applications that require quick retrieval of large datasets.

In terms of technology, these drives utilize the Serial Attached SCSI (SAS) interface, which is favored in enterprise settings for its reliability and speed. SAS provides better performance than traditional SATA drives, particularly when dealing with high workloads, as it supports multiple concurrent connections and higher data throughput.

The ST936701SS and ST973401SS are also equipped with advanced features such as Seagate's Native Command Queuing (NCQ), which optimizes the order in which read and write commands are executed. This results in improved performance under multi-tasking conditions, essential for enterprise servers managing multiple requests simultaneously.

Additionally, both drives incorporate features aimed at enhancing data integrity and reliability. They support End-to-End Data Protection and are designed to endure the rigors of continuous operation, with MTBF (Mean Time Between Failures) ratings that bolster their reputation for durability.

Energy efficiency is another notable characteristic, as both drives are designed to reduce power consumption without sacrificing performance. This is particularly important in enterprise environments where power management contributes to lower operational costs.

In conclusion, the Seagate ST936701SS and ST973401SS drives are robust, reliable storage solutions tailored for enterprise applications. With their high performance, advanced technology features, and capacity options, they provide organizations with the scalability and efficiency required in today’s data-driven landscape. Whether it's for critical data management tasks or high-access applications, these drives stand out as a solid choice for any enterprise storage strategy.
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