Error recovery control: Difference between revisions

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'''Time-Limited Error Recovery''' (TLER) is a solutionname designedused by [[Western Digital]] thatfor allowsa [[AT_Attachment|PATAhard drive]] andfeature [[SATA]]that [[hardallows disks]]improved toerror behandling usedin witha [[RAID]] controllersenvironment. ThisIn featuresome willcases, preventthere is a diskconflict fromwhether beingerror markedhandling failedshould bybe limitingundertaken by the timehard spentdrive on correcting detected errors causedor by vibrations during high loads. This feature reduces the chanceRAID of data losscontroller, which happensleads whento multipledrives disksbeing failmarked whileas theunusable RAIDand volumesignificant isperformance indegradation, degraded mode. Western Digital's RAID edition hard disks come withwhen this featurecould enabledotherwise byhave default,been with their other disks having the option disabled by default or completely unsupportedavoided. TLERA cansimilar betechnology enabledcalled or'''Error disabledRecovery usingControl''' the(ERC) toolis WDTLERused onby acompetitor DOS bootdisk[[Seagate]].

==Overview==

Western Digital states that this feature cannot be disabled. [http://wdc.custhelp.com/cgi-bin/wdc.cfg/php/enduser/std_adp.php?p_faqid=1478] However users and independed editors have have reported that this feature can be disabled. [http://techreport.com/reviews/2006q3/wd-500s/index.x?pg=1] [http://www.silentpcreview.com/forums/viewtopic.php?t=38385&sid=16f0f601b1174a4ebf3fd6fd295b2351] [http://www.fatwallet.com/forums/messageview.php?catid=18&threadid=660910&start=0] [http://www.anandtech.com/storage/showdoc.aspx?i=2922] The tool allows this feature to be disabled by setting the values for read and write and 0 second. By default, Caviar Raid Edition comes with read disabled and write set to 7 seconds while both settings are disabled for Raptor hard disks.

Modern [[hard drive]]s feature an ability to recover from some read/write errors by internally remapping [[sector]]s and 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. [[RAID]] controllers are designed to recognize a drive which does not respond within a few seconds, and mark it as unreliable, indicating that it should be withdrawn from use and the [[RAID array|array]] rebuilt from [[parity data]]. This is a long process, degrades performance, and if a second drive should fails under the resulting additional workload, it can be catastrophic.

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.

==TLER in a non-RAID environment==

Effectively, TLER and similar features limit the performance of on-drive error handling, to allow RAID controllers to handle the error if problematic. In a non-RAID environment, such features are unhelpful, and manufacturers do not recommend their use.

TLER can be enabled or disabled on certain Western Digital drives, using the tool WDTLER on a DOS bootdisk. Western Digital states that this feature cannot be disabled. [http://wdc.custhelp.com/cgi-bin/wdc.cfg/php/enduser/std_adp.php?p_faqid=1478] However users and independed editors have have reported that this feature can be disabled. [http://techreport.com/reviews/2006q3/wd-500s/index.x?pg=1] [http://www.silentpcreview.com/forums/viewtopic.php?t=38385&sid=16f0f601b1174a4ebf3fd6fd295b2351] [http://www.fatwallet.com/forums/messageview.php?catid=18&threadid=660910&start=0] [http://www.anandtech.com/storage/showdoc.aspx?i=2922] The tool allows this feature to be disabled by setting the values for read and write and 0 second. By default, Caviar Raid Edition comes with read disabled and write set to 7 seconds while both settings are disabled for Raptor hard disks.

==External links==