Error recovery control: Difference between revisions

Revision as of 02:10, 8 October 2016

Revision as of 02:47, 8 October 2016

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Modern [[hard drive]]s feature an ability to recover from some read/write errors by internally remapping [[Disk sector|sectors]] and performing other forms of self test and recovery. The process for this can sometimes take several seconds or (under heavy usage) minutes, during which time the drive is unresponsive. Hardware RAID controllers and software RAID implementations are designed to recognise a drive which does not respond within a few seconds, and mark it as unreliable, indicating that it should be withdrawn from use and the array rebuilt from [[Parity bit#Parity block|parity data]]. This is a long process, degrades performance, and if more drives fail under the resulting additional workload, it may be catastrophic.

If the drive itself isn'tis inherently reliable but has some bad sectors, then TLER and similar features prevent a disk from being unnecessarily marked as 'failed' by limiting the time spent on correcting detected errors before advising the array controller of a failed operation. The array controller can then handle the data recovery for the limited amount involved, rather than marking the entire drive as faulty.

==Desktop computers and TLER==