Hdparm - Revision history

Leo: /* Secure Erase */

2024-01-20T22:44:26Z

Secure Erase

← Older revision		Revision as of 22:44, 20 January 2024
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	=== Secure Erase ===		=== Secure Erase ===
	See: [[~~Securely Erasing a Disk~~]]		See: [[Securely_Erasing_a_Disk#ATA_Secure_Erase]]

	===Fix a damaged sector by forcing reallocation===		===Fix a damaged sector by forcing reallocation===

Leo: /* Tasks */

2021-04-03T20:08:16Z

Tasks

← Older revision		Revision as of 20:08, 3 April 2021
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	==Tasks==		==Tasks==

			=== Secure Erase ===
			See: [[Securely Erasing a Disk]]

	===Fix a damaged sector by forcing reallocation===		===Fix a damaged sector by forcing reallocation===

Leo: /* Fix a bad sector by forcing reallocation */

2021-04-03T04:20:08Z

Fix a bad sector by forcing reallocation

← Older revision		Revision as of 04:20, 3 April 2021
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	==Tasks==		==Tasks==

	===Fix a ~~bad~~ sector by forcing reallocation===		===Fix a damaged sector by forcing reallocation===
	All modern hard drives have a small set of reserved sectors that can be reallocated (or mapped to) by bad sectors as they are detected. This is usually a transparent process ~~but sometimes requires~~ some manual intervention. Typically, bad sectors will present itself as a device that can't be read or written to at a specific location. Another good clue would be having <code>dd</code> result in an "Input/output error". The Linux kernel would also complain similar to the following (from <code>dmesg</code>):		All modern hard drives have a small set of reserved sectors that can be reallocated (or mapped to) by bad sectors as they are detected by the disk firmware. This is usually a transparent process and only happens when the sector is written to. However, because of how filesystems (and possibly the kernel?) functions, it may require some manual intervention with <code>hdparm</code> which we'll go into details below.

			Typically, bad sectors will present itself as a device that can't be read or written to at a specific location which results in the filesystem being mounted as read-only or the disk being dropped from a RAID array. Another good clue would be having <code>dd</code> result in an "Input/output error". The Linux kernel would also complain similar to the following (from <code>dmesg</code>):
	{{Highlight		{{Highlight
	\| code = [Fri Apr 2 20:47:18 2021] sd 2:0:0:0: [sdb] tag#11 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE		\| code = [Fri Apr 2 20:47:18 2021] sd 2:0:0:0: [sdb] tag#11 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE

Leo at 04:14, 3 April 2021

2021-04-03T04:14:30Z

← Older revision		Revision as of 04:14, 3 April 2021
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	hdparm can be used to on any mass storage device.		hdparm can be used to on any mass storage device.

	===~~Disk Information~~===		===Get disk information===
	Use <code>hdparm -I /dev/disk</code> to show hardware properties of the device.		Use <code>hdparm -I /dev/disk</code> to show hardware properties of the device.
	{{Highlight		{{Highlight
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	==Tasks==		==Tasks==

	===~~Repair~~ a bad sector===		===Fix a bad sector by forcing reallocation===
	~~If you~~ have a bad ~~sector that the disk~~ is ~~unable to read~~, ~~you~~ can ~~use~~ <code>~~hdparm~~</code> to ~~write to a specific sector which will hopefully cause~~ the ~~disk to remap the bad sector to a good~~ sector. ~~This process is done transparently by the disk's firmware and the number~~ of ~~bad~~ sectors ~~that have been reallocated can~~ be ~~seen under~~ the <code>~~Reallocated_Sector_Ct~~</code> ~~parameter on SMART.~~		All modern hard drives have a small set of reserved sectors that can be reallocated (or mapped to) by bad sectors as they are detected. This is usually a transparent process but sometimes requires some manual intervention. Typically, bad sectors will present itself as a device that can't be read or written to at a specific location. Another good clue would be having <code>dd</code> result in an "Input/output error". The Linux kernel would also complain similar to the following (from <code>dmesg</code>):
			{{Highlight
	~~Given~~ the following ~~message, we know that LBA 4005685760 is bad~~:{{Highlight\|lang=text\|code=SMART Self-test log structure revision number 1		\| code = [Fri Apr 2 20:47:18 2021] sd 2:0:0:0: [sdb] tag#11 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
			[Fri Apr 2 20:47:18 2021] sd 2:0:0:0: [sdb] tag#11 Sense Key : Medium Error [current]
			[Fri Apr 2 20:47:18 2021] sd 2:0:0:0: [sdb] tag#11 Add. Sense: Unrecovered read error - auto reallocate failed
			[Fri Apr 2 20:47:18 2021] sd 2:0:0:0: [sdb] tag#11 CDB: Read(16) 88 00 00 00 00 00 00 00 02 08 00 00 01 f8 00 00
			[Fri Apr 2 20:47:18 2021] print_req_error: I/O error, dev sdb, sector 1000 flags 0
			\| lang = text
			}}
			Bad sectors can also be found with SMART tests. The LBA of any problematic sectors will be displayed with the <code>smartctl -a</code> output and will look something similar to the following under the self-test section:{{Highlight\|lang=text\|code=SMART Self-test log structure revision number 1
	Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error		Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error
	1 Extended offline Completed: read failure 40% 12786 4005685760}}We can ~~confirm this by attempting to~~ read ~~that sector with~~ <code>dd</code> or <code>hdparm</code>:		1 Extended offline Completed: read failure 40% 12786 4005685760}}Knowing which sectors are bad allows us to try making the drive firmware be aware of the issue and allow it to reallocate the bad sector. We can force a low level sector read or write using the <code>hdparm</code> utility. We can try reading the bad sector with <code>hdparm</code> to confirm the issue:{{Highlight
	{{Highlight		\| code = # hdparm --read-sector 4005685760 /dev/sdb
	\| code = ~~# dd if=/dev/sdb of=/dev/null skip=4005685760 bs=512 conv=sync~~
	~~dd: error reading '/dev/sdb': Input/output error~~

	# hdparm --read-sector 4005685760 /dev/sdb
	/dev/sdb:		/dev/sdb:
	reading sector 4005685760: FAILED: Input/output error		reading sector 4005685760: FAILED: Input/output error
	\| lang = terminal		\| lang = terminal
	}}		}}
	~~Using~~ <code>hdparm</code>, ~~we can write~~ to ~~this specific sector by issuing low-level~~ write ~~command directly~~ to ~~the disk~~.		W can try to remap the bad sector by writing to this specific sector with <code>hdparm</code>. The drive may take some time to reallocate. If this fails with an error, something else far worse than bad sectors is probably wrong with the drive. Usually, bad sectors come consecutively and it may help to write to a range of sectors. <code>hdparm</code> doesn't appear to support this, but can be worked around using a loop in bash:
	{{Highlight		{{Highlight
	\| code = # hdparm --write-sector 4005685760 --yes-i-know-what-i-am-doing /dev/sdb		\| code = # hdparm --write-sector 4005685760 --yes-i-know-what-i-am-doing /dev/sdb
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	\| lang = terminal		\| lang = terminal
	}}		}}
	~~It may take <code>hdparm</code> some time before showing the success message if the disk needs to reallocate the sector.~~ If the corrupt sector was reallocated, you should see both the <code>Reallocated_Sector_Ct</code> and <code>Reallocated_Event_Count</code> value increase and the <code>Current_Pending_Sector</code> decrease.		If the corrupt sector was reallocated, you should see both the <code>Reallocated_Sector_Ct</code> and <code>Reallocated_Event_Count</code> value increase and the <code>Current_Pending_Sector</code> decrease in the SMART report (ie. from <code>smartctl -a /dev/sdb</code>). Your goal is to try writing to the disk using <code>hdparm</code> until <code>Current_Pending_Sector</code> becomes 0.<br /> {{Navbox Linux}}
	~~After writing~~ to ~~a sector and forcing a sector reallocation,~~ try writing to the disk ~~with~~ <code>dd</code>~~. If you continue to experience errors, try rewriting the sectors near where the error took place and then try again~~.<br />{{Navbox Linux}}
	[[Category:Linux]]		[[Category:Linux]]
	[[Category:LinuxUtilities]]		[[Category:LinuxUtilities]]

Leo: /* Repair a bad sector */

2021-04-03T03:28:17Z

Repair a bad sector

← Older revision		Revision as of 03:28, 3 April 2021
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	\| lang = terminal		\| lang = terminal
	}}		}}
	It may take <code>hdparm</code> some time before showing the success message if the disk needs to reallocate the sector. If the corrupt sector was reallocated, you should see both the <code>Reallocated_Sector_Ct</code> and <code>Reallocated_Event_Count</code> value increase and the <code>Current_Pending_Sector</code> decrease. ~~If this didn't happen~~ and ~~if your~~ disk ~~still can't read that particular sector~~ with ~~either~~ <code>dd</code> ~~or <code>hdparm</code>~~, then ~~something else really bad happened with your disk~~.		It may take <code>hdparm</code> some time before showing the success message if the disk needs to reallocate the sector. If the corrupt sector was reallocated, you should see both the <code>Reallocated_Sector_Ct</code> and <code>Reallocated_Event_Count</code> value increase and the <code>Current_Pending_Sector</code> decrease.
			After writing to a sector and forcing a sector reallocation, try writing to the disk with <code>dd</code>. If you continue to experience errors, try rewriting the sectors near where the error took place and then try again.<br />{{Navbox Linux}}

	<br />{{Navbox Linux}}
	[[Category:Linux]]		[[Category:Linux]]
	[[Category:LinuxUtilities]]		[[Category:LinuxUtilities]]

Leo: /* Repair a bad sector */

2021-04-03T03:23:47Z

Repair a bad sector

← Older revision		Revision as of 03:23, 3 April 2021
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	\| lang = terminal		\| lang = terminal
	}}		}}
	Using <code>hdparm</code>, we can write to this specific sector by issuing low-level write command directly to the disk~~. If the sector is indeed bad, the disk will reallocate the sector transparently, though sometimes with a long delay~~.		Using <code>hdparm</code>, we can write to this specific sector by issuing low-level write command directly to the disk.
	{{Highlight		{{Highlight
	\| code = ~~# dd if=/dev/zero of=/dev/sdb skip=4005685760 bs=512 count=1 conv=sync~~		\| code = # hdparm --write-sector 4005685760 --yes-i-know-what-i-am-doing /dev/sdb
	~~## This may reallocate the bad sector, but not always. It may just return an Input/Output error.~~

	# hdparm --write-sector 4005685760 --yes-i-know-what-i-am-doing /dev/sdb
	## This could take some time if the disk needs to reallocate the sector.		## This could take some time if the disk needs to reallocate the sector.
	/dev/sdb:		/dev/sdb:
	re-writing sector 4005685760: succeeded		re-writing sector 4005685760: succeeded

			## In cases where you think there's a range of bad sectors, you can do something like:
			# for i in {1000..1010} ; do echo $i ; hdparm --write-sector $i --yes-i-know-what-i-am-doing /dev/sdb ; done
	\| lang = terminal		\| lang = terminal
	}}		}}
	It may take <code>hdparm</code> some time before showing the success message if the disk needs to reallocate the sector. If the corrupt sector was reallocated, you should see both the <code>Reallocated_Sector_Ct</code> and <code>Reallocated_Event_Count</code> value increase and the <code>Current_Pending_Sector</code> decrease. If this didn't happen and if your disk still can't read that particular sector with either <code>dd</code> or <code>hdparm</code>, then something else really bad happened with your disk.		It may take <code>hdparm</code> some time before showing the success message if the disk needs to reallocate the sector. If the corrupt sector was reallocated, you should see both the <code>Reallocated_Sector_Ct</code> and <code>Reallocated_Event_Count</code> value increase and the <code>Current_Pending_Sector</code> decrease. If this didn't happen and if your disk still can't read that particular sector with either <code>dd</code> or <code>hdparm</code>, then something else really bad happened with your disk.


	<br />{{Navbox Linux}}		<br />{{Navbox Linux}}
	[[Category:Linux]]		[[Category:Linux]]
	[[Category:LinuxUtilities]]		[[Category:LinuxUtilities]]

Leo: /* Repair a bad sector */

2021-04-03T03:22:23Z

Repair a bad sector

Show changes

Leo at 00:13, 1 August 2020

2020-08-01T00:13:55Z

← Older revision		Revision as of 00:13, 1 August 2020
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	Something's wonky with this...		Something's wonky with this...

			{{Navbox Linux}}
			[[Category:Linux]]
			[[Category:LinuxUtilities]]

Leo at 00:10, 1 August 2020

2020-08-01T00:10:49Z

@@ Line 1: / Line 1: @@
 hdparm is a disk utility that allows for low level commands to be sent to the storage device.
-==Repair a bad sector==
+== Usage ==
 If you have a bad sector that the disk is unable to read, you can use hdparm to write to a specific sector which will hopefully cause the disk to remap the bad sector to a good sector. This process is done transparently by the disk's firmware and the number of bad sectors that have been reallocated can be seen under the <code>Reallocated_Sector_Ct</code> parameter on SMART.

Leo: /* Repair a bad sector */

2020-07-31T18:57:24Z

Repair a bad sector

← Older revision		Revision as of 18:57, 31 July 2020
Line 1:		Line 1:
	hdparm is a disk utility that allows for low level commands to be sent to the storage device.		hdparm is a disk utility that allows for low level commands to be sent to the storage device.

	== Repair a bad sector ==		==Repair a bad sector==
	If you have a bad sector that the disk is unable to read, you can use hdparm to write to a specific sector which will hopefully cause the disk to remap the bad sector to a good sector. This process is done transparently by the disk's firmware and the number of bad sectors that have been reallocated can be seen under the <code>Reallocated_Sector_Ct</code> parameter on SMART.		If you have a bad sector that the disk is unable to read, you can use hdparm to write to a specific sector which will hopefully cause the disk to remap the bad sector to a good sector. This process is done transparently by the disk's firmware and the number of bad sectors that have been reallocated can be seen under the <code>Reallocated_Sector_Ct</code> parameter on SMART.

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	0000 0000 0000 0000 0000 0000 0000 0000		0000 0000 0000 0000 0000 0000 0000 0000
	\| lang = terminal		\| lang = terminal
	}}		}}But the reallocate sector count didn't increase...

			Something's wonky with this...