Error recovery control: Difference between revisions

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If the drive itself is 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.

==Typical defaults==

==Desktop computers and TLER==

Effectively, TLER and similar features limit the performance of on-drive error handling, to allow hardware RAID controllers and software RAID implementations to handle the error if problematic.

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=== ZFS ===

The [[ZFS|ZFS filesystem]] was writtendesigned to immediately write data to a sector that reports as bad or takes an excessively long time to read (such as non-TLER drives); this will usually force an immediate sector remap on a weak sector in most drives.{{Citation needed|date=March 2022}}

===RAID controllers===

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Linux [[mdadm]] simply holds and lets the drive complete its recovery – however, the default command timeout for the SCSI Disk layer (/sys/block/sd?/device/timeout) is 30 seconds,<ref>{{cite web|url=https://github.com/torvalds/linux/blob/master/drivers/scsi/sd.h#LC12|title=linux/sd.h at master · torvalds/linux · GitHub|work=GitHub}}</ref> after which it will attempt to reset the drive, and if that fails, put the drive offline.<ref>{{cite web|url=https://www.kernel.org/doc/html/v5.9/scsi/scsi_eh.html|title= Linux SCSI Subsystem: SCSI EH|work=kernel.org}}</ref>

== Changing ERC ==

== Western Digital Time Limit Error Recovery utility ==

===ATA-8 standard===

{{Unreferenced section|date=April 2019}}

The 2006 ATA-8 standard defines a SCT {{tt|Error Recovery Control}} command.<ref>[https://www.singlix.org/trdos/8086/archive/specs/D1699r3e-ATA8_ACS.pdf ATA/ATAPI Command Set (ATA8-ACS) ]</ref> For hard drives that implement this interface, the {{Mono|smartctl}} utility (part of the [[smartmontools]] package) can be used to change the error-recovery timeout via {{code|-l scterc}}.<ref name=greg>{{Cite web |author=Richard Gregory |url=http://abatis.org.uk/projects/erc/ |title=Author's description of the original patch to smartctl that implemented that feature |access-date=2013-02-15 |archive-url=https://web.archive.org/web/20130910034510/http://cgi.csc.liv.ac.uk:80/~greg/projects/erc/ |archive-date=2013-09-10 |url-status=live }}</ref> In 2018, ACS-4 added a functionality for the setting to persist across reboot; it is now supported by smartctl.<ref>{{cite web |title=#1427 (Add support for SCT Error Recovery Timer features added in ACS-4) – smartmontools |url=https://www.smartmontools.org/ticket/1427 |website=www.smartmontools.org}}</ref>

The {{Mono|WDTLER.EXE}} utility allows for the enabling or disabling of the TLER parameter in the hard disk's firmware settings allowing the user to determine the best setting for his particular usage as either a stand-alone or RAID drive. This utility is written for [[DOS]] and you will require a DOS bootable disk with this utility on it to use it.

Controlling the TLERtimeout behavior through the {{Mono|smartctl}} utility may not work on all hard disk drives because some manufacturers have changed their desktop drives not to include the support for the ERC parameter,<ref>{{cite web|url=http://www.spinics.net/lists/raid/msg38964.html|title=Re: md RAID with enterprise-class SATA or SAS drives|work=spinics.net}}</ref><ref>{{cite web|url=http://knowledge.seagate.com/articles/en_US/FAQ/203991en|title=Seagate FAQ: What is Error Recovery Control?|work=seagate.com}}</ref> purportedly to force sales of their more expensive RAID/enterprise models.{{Citation needed|date=April 2016}} Richard Gregory, who wrote the original ERC patch for smartctl, reports that Western Digital retracted ERC support by releasing a new model without notice.<ref name=greg/>

The utility works on and makes changes to all compatible Western Digital hard disk drives connected to the computer. It is important to remember that any change will affect all the hard drives. If you only wish to change specific hard drives on your computer then you should disconnect the other hard drives before you use this utility, then reconnect them after you are finished.

On Windows, the HDAT2 program is available in addition to smartctl (which is cross-platform).<ref name=greg/>

The utility comes with three batch files, {{Mono|TLERSCAN.BAT}} to get the current state of the TLER setting on all the hard drives, {{Mono|TLER-ON.BAT}} to enable TLER, and {{Mono|TLER-OFF.BAT}} to disable TLER. The included {{Mono|TLER-ON.BAT}} will set the Read & Write TLER time to seven seconds. If you wish to use a custom timeout value, you can use the {{Mono|WDTLER.EXE}} utility directly with the <code>-r# -w#</code> parameters to specify how many seconds the Time Limit value should be.

=== SCSI standard ===

Western Digital claims that using the {{Mono|WDTLER.EXE}} utility on newer drives can damage the firmware and make the disk unusable. The utility is no longer available from Western Digital, and new drives will not be able to have the TLER setting changed. RE disks are only suitable for RAID arrays and Caviar are only suitable for non-RAID use. The utility still{{When|date=April 2019}} works for older drives.

SBC-4 describes a RECOVERY TIME LIMIT field in the Read-Write Error Recovery mode page used to define how the drive performs error recovery.<ref>{{cite web |title=INCITS 506-202x - Information technology - SCSI Block Commands - 4 (SBC-4) draft revision 22 |url=https://standards.incits.org/apps/group_public/download.php/124286/livelink |access-date=22 May 2023 |date=15 September 2020}}</ref> The sdparm program can change this setting with {{code|1=--set=RTL}}.<ref>{{man|8|sdparm|Linux}}</ref>

=== Vendor utilities ===

==smartctl utility==

==== Western Digital ====

The {{Mono|smartctl}} utility (part of the smartmontools package) can be used<ref>{{Cite web |url=http://cgi.csc.liv.ac.uk/~greg/projects/erc/ |title=Author's description of the original patch to smartctl that implemented that feature |access-date=2013-02-15 |archive-url=https://web.archive.org/web/20130910034510/http://cgi.csc.liv.ac.uk:80/~greg/projects/erc/ |archive-date=2013-09-10 |url-status=dead }}</ref> on hard disk drives that fully implement the ATA-8<ref>[http://www.t13.org/documents/UploadedDocuments/docs2007/D1699r4a-ATA8-ACS.pdf AT Attachment 8 – ATA/ATAPI Command Set (ATA8-ACS) ]</ref> standard to control the TLER behavior by setting the SCT Error Recovery

A {{Mono|WDTLER.EXE}} utility allows the enabling or disabling of the TLER parameter on Western Digital hard drives. This utility is written for [[DOS]]. The utility works on and makes changes to all compatible Western Digital hard disk drives connected to the computer. The change survives power-cycling. Western Digital used to mention the tool in an FAQ.<ref name=customer-service>{{cite web |title=TLER / CCTL / ERC thread |url=https://hardforum.com/threads/tler-cctl-erc-thread.1562128/ |website=[H]ard{{!}}Forum |date=16 November 2010}}</ref>

Control ('''scterc''') parameter.

The utility comes with three batch files, {{Mono|TLERSCAN.BAT}} to get the current state of the TLER setting on all the hard drives, {{Mono|TLER-ON.BAT}} to enable TLER, and {{Mono|TLER-OFF.BAT}} to disable TLER. The included {{Mono|TLER-ON.BAT}} will set the Read & Write TLER time to seven seconds. IfIt youis wishpossible to use a custom timeout value, you can use the {{Mono|WDTLER.EXE}} utility directly with the <code>-r# -w#</code> parameters tofor specifya howcustom many seconds the Time Limit value should betimeout.

Controlling the TLER behavior through the {{Mono|smartctl}} utility may not work on all hard disk drives because some manufacturers have changed their desktop drives not to include the support for the ERC parameter,<ref>{{cite web|url=http://www.spinics.net/lists/raid/msg38964.html|title=Re: md RAID with enterprise-class SATA or SAS drives|work=spinics.net}}</ref><ref>{{cite web|url=http://knowledge.seagate.com/articles/en_US/FAQ/203991en|title=Seagate FAQ: What is Error Recovery Control?|work=seagate.com}}</ref> purportedly to force sales of their more expensive RAID/enterprise models.{{Citation needed|date=April 2016}}

Western Digital claims that using the {{Mono|WDTLER.EXE}} utility on newer drives can damage the firmware and make the disk unusable. The utility is no longer available from Western Digital, and new drives will not be able to have the TLER setting changed. RE disks are only suitable for RAID arrays and Caviar are only suitable for non-RAID use. The utility still works for older drives{{Whenwhich|date=AprilMay 20192023}}<!-- workswhat foris olderthe drivescutoff? -->.

==== Hitachi ====

Hitachi customer service stated in 2009 that there is a Feature Tool for changing ERC (referred to as CCTL).<ref name=customer-service/>

==== Seagate ====

Seagate provides a {{Mono|openSeaChest}} utility to allow you to interrogate and change many firmware settings including TLER. If you cannot use <code>smartctl -l scterr,x,y</code> to set the TLER, the relevant command-line commands are <code>openSeaChest_Configure -d /dev/sg0 --sctReadTimer</code> and <code>openSeaChest_Configure -d /dev/sg0 --sctWriteTimer</code>.

==References==

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==External links==

* [https://raid.wiki.kernel.org/index.php/Timeout_Mismatch Linux Raid wiki: Timeout Mismatch]

* [https://archive.today/20130121054825/http://wdc.custhelp.com/app/answers/detail/a_id/1397/p/227,283/session/L3RpbWUvMTMyMTQzOTc4NS9zaWQvdVhvYmpmSms%3D Western Digital FAQ answer ID 1397: Difference between Desktop edition and RAID (Enterprise) edition drives]

* [http://www.wdc.com/wdproducts/library/other/2579-001098.pdf Time-Limited Error Recovery (TLER) Information Sheet], Western Digital, January 2013

* [https://web.archive.org/web/20071103042201/http://www.samsung.com/global/business/hdd/learningresource/whitepapers/LearningResource_CCTL.html Samsung CCTL]