9.2DRIVE ERROR RECOVERY PROCEDURES

When an error occurs during drive operation, the drive performs error recovery procedures to attempt to recover the data. The error recovery procedures used are not user changeable.

9.3SAS SYSTEM ERRORS

Information on the reporting of operational errors across the interface is given in the SAS Interface Manual. The SSP Response returns information to the host about numerous kinds of errors. The Receive Diagnostic Results reports the results of diagnostic operations performed by the drive.

Status returned by the drive to the initiator is described in the SAS Interface Manual. Status reporting plays a role in systems error management and its use in that respect is described in sections where the various commands are discussed.

9.4BACKGROUND MEDIA SCAN

Background Media Scan (BMS) is a self-initiated media scan. BMS is defined in the T10 document SPC-4 available from the T10 committee. BMS performs reads across the entire addressable space of the media while the drive is idle. In RAID arrays, BMS allows hot spare drives to be scanned for defects prior to being put into service by the host system. On regular duty drives, if the host system makes use of the BMS Log Page, it can avoid placing data in suspect locations on the media. Unreadable and recovered error sites will be logged and reallocated.

With BMS, the host system can consume less power and system overhead by only checking BMS status and results rather than tying up the bus and consuming power in the process of host-initiated media scanning activity.

Since the background scan functions are only done during idle periods, BMS causes a negligible impact to system performance. The BMS scan is performed after 500ms of idle time. Other features that normally use idle time to function will function normally because BMS functions for bursts of 500ms and then suspends activity for 100ms to allow other background functions to operate.

BMS interrupts immediately to service host commands from the interface bus while performing reads. BMS will complete any BMS-initiated error recovery prior to returning to service host-initiated commands. Overhead associated with a return to host-servicing activity from BMS only impacts the first command that interrupted BMS, this results in a typical delay of about 1ms.

9.5AUTO-REALLOCATION

Auto-Reallocation allows the drive to reallocate unreadable locations on a subsequent write command if the recovery process deems the location to be defective. The drive performs auto-reallocation on every WRITE command. With each write to a Logical LBA, the drive writes the data to a different physical media location. Physical locations that return unrecoverable errors are retired during future WRITE attempts and associated recovery process.

This is in contrast to the system having to use the REASSIGN BLOCKS command to reassign a location that was unreadable and then generate a WRITE command to rewrite the data. This operation requires that AWRE and ARRE are enabled—this is the default setting from the Seagate factory.

PULSAR.2 SAS PRODUCT MANUAL, REV. C

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Seagate ST800FM0002, ST100FM0012, ST100FM0052, ST100FM0002, ST200FM0012, ST200FM0002 manual Drive Error Recovery Procedures
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ST800FM0002, ST100FM0002, ST200FM0002, ST400FM0012, ST800FM0032 specifications

The Seagate ST100FM0012, ST800FM0012, ST400FM0042, ST400FM0002, and ST100FM0052 are high-performance hard drives designed for enterprise applications, offering advanced features and reliability for demanding workloads.

The ST100FM0012 is a 10TB hard drive that strikes a balance between capacity and performance. It utilizes a 7200 RPM spindle speed and features a 256MB cache, enabling efficient data access and enhanced read/write performance. With Seagate’s AgileArray technology, the ST100FM0012 is optimized for NAS environments, providing multi-drive reliability and error recovery.

The ST800FM0012 is an 8TB variant that shares many features with its 10TB counterpart but is tailored for organizations needing robust storage without reaching the highest tier of capacity. Its dual-plane rotational vibration technology minimizes vibration in multi-drive systems, ensuring sustained performance over prolonged use. This makes it an excellent choice for virtualization and data-intensive applications.

The ST400FM0042 offers a 4TB capacity suited for smaller enterprise needs or as a backup solution. With an impressive performance profile, including a 7200 RPM speed and 128MB cache, it accommodates both sequential and random workloads with ease. This drive stands out with its PowerChoice technology, allowing users to manage power consumption and reduce operational costs.

Another 4TB option, the ST400FM0002, is particularly designed for hybrid configurations, pairing the fast access of the hard drive with the speed of SSDs. It features Seagate's advanced thermal management technologies, ensuring optimal operating temperatures and performance stability during intensive workloads.

The ST100FM0052 rounds out the lineup with a 10TB capacity but is specifically aimed at surveillance applications. It supports a workload rate of 180TB per year, making it ideal for always-on recording scenarios. The drive is built with optimized firmware, which ensures enhanced performance in write-intensive environments, essential for video recording and security systems.

All these drives are equipped with Seagate’s proprietary technologies, including data recovery services and built-in data protection features, ensuring data integrity and security. The drives are built for durability, reliability, and high performance in mission-critical environments, making them indispensable components of modern enterprise data storage solutions. With capacities ranging from 4TB to 10TB, they cater to varying storage needs across different sectors.
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