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HDPARM(8)		    System Manager's Manual		     HDPARM(8)

       hdparm - get/set SATA/IDE device parameters

       hdparm [options] [device ...]

       hdparm  provides	 a command line interface to various kernel interfaces
       supported by the Linux SATA/PATA/SAS "libata" subsystem and  the	 older
       IDE driver subsystem.  Many newer (2008 and later) USB drive enclosures
       now also support "SAT" (SCSI-ATA Command Translation) and therefore may
       also  work  with	 hdparm.   E.g. recent WD "Passport" models and recent
       NexStar-3 enclosures.  Some options may work correctly  only  with  the
       latest kernels.

       When  no	 options  are  given,  -acdgkmur  is  assumed.	 For "Get/set"
       options, a query without the optional parameter (e.g.  -d)  will	 query
       (get)  the  device state, and with a parameter (e.g., -d0) will set the
       device state.

       -a     Get/set sector count for filesystem (software) read-ahead.  This
	      is  used	to  improve  performance  in sequential reads of large
	      files, by prefetching additional blocks in anticipation of  them
	      being  needed  by the running task.  Many IDE drives also have a
	      separate	built-in  read-ahead  function,	 which	augments  this
	      filesystem (software) read-ahead function.

       -A     Get/set  the  IDE	 drive's read-lookahead feature (usually ON by
	      default).	 Usage: -A0 (disable) or -A1 (enable).

       -b     Get/set bus state.

       -B     Get/set Advanced Power Management feature, if the drive supports
	      it.  A  low  value  means aggressive power management and a high
	      value means better performance.  Possible	 settings  range  from
	      values  1	 through  127 (which permit spin-down), and values 128
	      through 254 (which do not permit spin-down).  The highest degree
	      of  power	 management  is	 attained with a setting of 1, and the
	      highest I/O performance with a setting of 254.  A value  of  255
	      tells  hdparm to disable Advanced Power Management altogether on
	      the drive (not all drives support disabling it, but most do).

       -c     Get/set (E)IDE 32-bit I/O support.  A numeric parameter  can  be
	      used  to enable/disable 32-bit I/O support.  Currently supported
	      values include 0 to disable 32-bit  I/O  support,	 1  to	enable
	      32-bit  data  transfers,	and  3 to enable 32-bit data transfers
	      with a special sync sequence required  by	 many  chipsets.   The
	      value  3	works  with nearly all 32-bit IDE chipsets, but incurs
	      slightly more overhead.	Note  that  "32-bit"  refers  to  data
	      transfers	 across	 a  PCI or VLB bus to the interface card only;
	      all (E)IDE drives still have only a 16-bit connection  over  the
	      ribbon cable from the interface card.

       -C     Check  the  current  IDE power mode status, which will always be
	      one  of  unknown	(drive	does  not   support   this   command),
	      active/idle  (normal  operation), standby (low power mode, drive
	      has spun down), or sleeping (lowest power mode,  drive  is  com-
	      pletely  shut down).  The -S, -y, -Y, and -Z options can be used
	      to manipulate the IDE power modes.

       -d     Get/set the "using_dma" flag for this drive.   This  option  now
	      works  with most combinations of drives and PCI interfaces which
	      support DMA and which are known to the kernel IDE driver.	 It is
	      also a good idea to use the appropriate -X option in combination
	      with -d1 to ensure that the drive itself is programmed  for  the
	      correct  DMA mode, although most BIOSs should do this for you at
	      boot time.  Using DMA nearly always gives the best  performance,
	      with  fast  I/O  throughput and low CPU usage.  But there are at
	      least a few configurations of chipsets and drives for which  DMA
	      does not make much of a difference, or may even slow things down
	      (on really messed up hardware!).	Your mileage may vary.

	      DCO stands for Device Configuration Overlay, a way  for  vendors
	      to  selectively disable certain features of a drive.  The --dco-
	      freeze option will freeze/lock the current drive	configuration,
	      thereby  preventing  software (or malware) from changing any DCO
	      settings until after the next power-on reset.

	      Query and dump information regarding  drive  configuration  set-
	      tings  which  can	 be  disabled  by the vendor or OEM installer.
	      These settings show capabilities of the  drive  which  might  be
	      disabled	by the vendor for "enhanced compatibility".  When dis-
	      abled, they are otherwise hidden and will not  show  in  the  -I
	      identify	output.	 For example, system vendors sometimes disable
	      48_bit addressing on large drives, for compatibility  (and  loss
	      of  capacity)  with a specific BIOS.  In such cases, --dco-iden-
	      tify will show that the drive is 48_bit capable, but -I will not
	      show it, and nor will the drive accept 48_bit commands.

	      Reset  all  drive	 settings, features, and accessible capacities
	      back to factory defaults and full	 capabilities.	 This  command
	      will  fail  if  DCO  is  frozen/locked, or if a -Np maximum size
	      restriction has also been set.  This is EXTREMELY DANGEROUS  and
	      will  very  likely  cause massive loss of data.  DO NOT USE THIS

	      Use the kernel's "O_DIRECT" flag when  performing	 a  -t	timing
	      test.   This  bypasses  the  page cache, causing the reads to go
	      directly from the drive into hdparm's buffers,  using  so-called
	      "raw"  I/O.  In many cases, this can produce results that appear
	      much faster than the usual page cache method,  giving  a	better
	      indication of raw device and driver performance.

	      causes hdparm to issue an IDENTIFY command to  the  kernel,  but
	      incorrectly marked as a "non-data" command.  This results in the
	      drive being left with its	 DataReQust(DRQ)  line	"stuck"	 high.
	      This confuses the kernel drivers, and may crash the system imme-
	      diately with massive data loss.  The option exists  to  help  in
	      testing  and  fortifying	the  kernel against similar real-world
	      drive malfunctions.  VERY DANGEROUS, DO NOT USE!!

       -D     Enable/disable the on-drive defect management  feature,  whereby
	      the  drive firmware tries to automatically manage defective sec-
	      tors by relocating them to "spare" sectors reserved by the  fac-
	      tory for such.  Control of this feature via the -D option is not
	      supported for most modern drives since ATA-4; thus this  command
	      may fail.

       -E     Set cd/dvd drive speed.  This is NOT necessary for regular oper-
	      ation, as the drive will automatically switch speeds on its own.
	      But  if  you  want  to  play with it, just supply a speed number
	      after the option, usually a number like 2 or  4.	 This  can  be
	      useful in some cases, though, to smooth out DVD video playback.

       -f     Sync  and	 flush	the buffer cache for the device on exit.  This
	      operation is also performed internally as part of the -t and  -T
	      timings and other options.

	      This  option  currently  works  only  on ext4 and xfs filesystem
	      types.  When used, this must  be	the  only  option  given.   It
	      requires	two  parameters:  the  desired file size in kilo-bytes
	      (byte count divided by 1024), followed by the pathname  for  the
	      new  file.  It will create a new file of the specified size, but
	      without actually having to write any data	 to  the  file.	  This
	      will  normally  complete very quickly, and without thrashing the
	      storage device.

	      E.g. Create a 10KByte file: hdparm --fallocate 10 temp_file

	      When used, this must be the only option given.   It  requires  a
	      file path as a parameter, and will print out a list of the block
	      extents (sector ranges) occupied by that file on	disk.	Sector
	      numbers  are given as absolute LBA numbers, referenced from sec-
	      tor 0 of the physical device rather than from the	 partition  or
	      filesystem.   This information can then be used for a variety of
	      purposes, such as examining the degree of fragmenation of larger
	      files,  or  determining appropriate sectors to deliberately cor-
	      rupt during fault-injection testing procedures.

	      This option uses the new FIEMAP (file extent map)	 ioctl()  when
	      available,  and  falls back to the older FIBMAP (file block map)
	      ioctl() otherwise.  Note	that  FIBMAP  suffers  from  a	32-bit
	      block-number  interface,	and  thus not work beyond 8TB or 16TB.
	      FIBMAP is also very slow, and does not deal well	with  preallo-
	      cated  uncommitted  extents  in  ext4/xfs	 filesystems, unless a
	      sync() is done before using this option.

	      When used, this should be the only option given.	It requires  a
	      file path immediately after the option, indicating where the new
	      drive firmware should be read from.  The contents of  this  file
	      will  be	sent  to the drive using the (S)ATA DOWNLOAD MICROCODE
	      command, using either transfer protocol 7 (entire file at once),
	      or,  if  the  drive  supports it, transfer protocol 3 (segmented
	      download).   This	 command  is  EXTREMELY	 DANGEROUS  and	 could
	      destroy both the drive and all data on it.  DO NOT USE THIS COM-
	      MAND.  The --fwdownload-mode3  ,	--fwdownload-mode3-max	,  and
	      --fwdownload-mode7  variations on basic --fwdownload allow over-
	      riding automatic protocol detection in favour of forcing	hdparm
	      to use a specific transfer protocol, for testing purposes only.

       -F     Flush  the  on-drive  write  cache  buffer (older drives may not
	      implement this).

       -g     Display the drive geometry (cylinders, heads, sectors), the size
	      (in sectors) of the device, and the starting offset (in sectors)
	      of the device from the beginning of the drive.

       -h     Display terse usage information (help).

       -H     Read the temperature from some (mostly  Hitachi)	drives.	  Also
	      reports  if  the temperature is within operating condition range
	      (this may not be reliable). Does not cause the drive to spin  up
	      if idle.

       -i     Display  the  identification info which the kernel drivers (IDE,
	      libata) have stored from boot/configuration time.	 This may dif-
	      fer  from	 the  current information obtainable directly from the
	      drive itself with the -I option.	The data returned may  or  may
	      not  be current, depending on activity since booting the system.
	      For a more detailed interpretation of the	 identification	 info,
	      refer  to	 AT  Attachment	 Interface  for	 Disk Drives, ANSI ASC
	      X3T9.2 working draft, revision 4a, April 19/93, and  later  edi-

	      Issue  an	 ATA  IDLE_IMMEDIATE  command, to put the drive into a
	      lower power state.  Usually the device remains spun-up.

	      Issue an ATA IDLE_IMMEDIATE_WITH_UNLOAD command,	to  unload  or
	      park the heads and put the drive into a lower power state.  Usu-
	      ally the device remains spun-up.

       -I     Request identification info directly from the  drive,  which  is
	      displayed in a new expanded format with considerably more detail
	      than with the older -i option.

	      This is a special variation on the -I option,  which  accepts  a
	      drive  identification block as standard input instead of using a
	      /dev/hd* parameter.  The format of this block  must  be  exactly
	      the  same as that found in the /proc/ide/*/hd*/identify "files",
	      or that produced by the --Istdout option described below.	  This
	      variation	 is  designed  for  use	 with collected "libraries" of
	      drive identification information, and can also be used on	 ATAPI
	      drives  which may give media errors with the standard mechanism.
	      When --Istdin is used, it must be the *only* parameter given.

	      This option dumps the drive's identify data in hex to stdout, in
	      a format similar to that from /proc/ide/*/identify, and suitable
	      for later use with the --Istdin option.

       -J     Get/set the Western Digital (WD) Green Drive's  "idle3"  timeout
	      value.   This  timeout  controls	how  often the drive parks its
	      heads and enters a low power  consumption	 state.	  The  factory
	      default  is  eight  (8) seconds, which is a very poor choice for
	      use with Linux.  Leaving it at the default will result  in  hun-
	      dreds  of	 thousands  of head load/unload cycles in a very short
	      period of time.  The drive mechanism is only rated  for  300,000
	      to  1,000,000  cycles, so leaving it at the default could result
	      in premature failure, not to mention the performance  impact  of
	      the drive often having to wake-up before doing routine I/O.

	      WD  supply  a WDIDLE3.EXE DOS utility for tweaking this setting,
	      and you should use that program instead of hdparm if at all pos-
	      sible.   The  reverse-engineered implementation in hdparm is not
	      as complete as the original official  program,  even  though  it
	      does  seem  to  work  on	at a least a few drives.  A full power
	      cycle is required for any change	in  setting  to	 take  effect,
	      regardless of which program is used to tweak things.

	      A setting of 30 seconds is recommended for Linux use.  Permitted
	      values are from 8 to 12 seconds, and from 30 to 300  seconds  in
	      30-second	 increments.   Specify	a value of zero (0) to disable
	      the WD idle3 timer completely (NOT RECOMMENDED!).

       -k     Get/set the "keep_settings_over_reset" flag for the drive.  When
	      this flag is set, the drive will preserve the -dmu settings over
	      a soft reset, (as done  during  the  error  recovery  sequence).
	      This  option defaults to off, to prevent drive reset loops which
	      could be caused by combinations of -dmu settings.	 The -k option
	      should  therefore	 only be set after one has achieved confidence
	      in correct system operation with a chosen set  of	 configuration
	      settings.	  In practice, all that is typically necessary to test
	      a configuration (prior to using -k) is to verify that the	 drive
	      can  be  read/written,  and that no error logs (kernel messages)
	      are generated in the process (look in /var/log/messages on  most

       -K     Set  the	drive's "keep_features_over_reset" flag.  Setting this
	      enables the drive to retain the settings for -APSWXZ over a soft
	      reset  (as  done	during	the error recovery sequence).  Not all
	      drives support this feature.

       -L     Set the drive's doorlock flag.  Setting this to 1 will lock  the
	      door mechanism of some removable hard drives (e.g. Syquest, ZIP,
	      Jazz..), and setting it to 0 will	 unlock	 the  door  mechanism.
	      Normally,	 Linux	maintains the door locking mechanism automati-
	      cally, depending on drive usage (locked whenever a filesystem is
	      mounted).	 But on system shutdown, this can be a nuisance if the
	      root partition is on a removable disk, since the root  partition
	      is  left	mounted (read-only) after shutdown.  So, by using this
	      command  to  unlock  the	door  after  the  root	filesystem  is
	      remounted	 read-only, one can then remove the cartridge from the
	      drive after shutdown.

       -m     Get/set sector count for multiple sector I/O on  the  drive.   A
	      setting  of  0 disables this feature.  Multiple sector mode (aka
	      IDE Block Mode), is a feature of most modern  IDE	 hard  drives,
	      permitting  the  transfer of multiple sectors per I/O interrupt,
	      rather than the usual one sector per interrupt.  When this  fea-
	      ture  is enabled, it typically reduces operating system overhead
	      for disk I/O by 30-50%.	On  many  systems,  it	also  provides
	      increased	 data  throughput  of  anywhere	 from 5% to 50%.  Some
	      drives, however (most notably the WD Caviar series), seem to run
	      slower with multiple mode enabled.  Your mileage may vary.  Most
	      drives support the minimum settings of 2, 4, 8, or 16 (sectors).
	      Larger settings may also be possible, depending on the drive.  A
	      setting of 16 or 32 seems optimal on many systems.  Western Dig-
	      ital  recommends	lower  settings	 of  4	to  8 on many of their
	      drives, due tiny (32kB) drive buffers and non-optimized  buffer-
	      ing  algorithms.	 The -i option can be used to find the maximum
	      setting supported by an installed drive (look for MaxMultSect in
	      the  output).   Some  drives claim to support multiple mode, but
	      lose data at some	 settings.   Under  rare  circumstances,  such
	      failures can result in massive filesystem corruption.

	      Deliberately  create  a  bad  sector (aka. "media error") on the
	      can  be  useful for testing of device/RAID error recovery mecha-
	      nisms.  The sector number is given as a (base10) parameter after
	      the  option.  Depending on the device, hdparm will choose one of
	      two possible  ATA	 commands  for	corrupting  the	 sector.   The
	      WRITE_LONG  works on most drives, but only up to the 28-bit sec-
	      tor boundary.  Some very recent drives (2008)  may  support  the
	      new  WRITE_UNCORRECTABLE_EXT  command, which works for any LBA48
	      sector.  If available, hdparm will use  that  in	preference  to
	      WRITE_LONG.  The WRITE_UNCORRECTABLE_EXT command itself presents
	      a choice of how the new bad sector should behave.	  By  default,
	      it  will	look like any other bad sector, and the drive may take
	      some time to retry and fail on subsequent READs of  the  sector.
	      However,	if a single letter f is prepended immediately in front
	      of the first digit of the sector number parameter,  then	hdparm
	      will issue a "flagged" WRITE_UNCORRECTABLE_EXT, which causes the
	      drive to merely flag the sector as bad  (rather  than  genuinely
	      corrupt  it), and subsequent READs of the sector will fail imme-
	      diately (rather than after several retries).  Note also that the
	      --repair-sector  option can be used to restore (any) bad sectors
	      when they are no longer needed, including sectors that were gen-
	      uinely bad (the drive will likely remap those to a fresh area on
	      the media).

       -M     Get/set Automatic Acoustic Management (AAM) setting. Most modern
	      harddisk	drives	have  the ability to speed down the head move-
	      ments to reduce their noise output.   The	 possible  values  are
	      between 0 and 254. 128 is the most quiet (and therefore slowest)
	      setting and 254 the fastest (and loudest). Some drives have only
	      two  levels (quiet / fast), while others may have different lev-
	      els between 128 and 254.	At the moment, most drives  only  sup-
	      port  3 options, off, quiet, and fast.  These have been assigned
	      the values 0, 128, and 254 at present, respectively, but integer
	      space  has  been	incorporated for future expansion, should this

       -n     Get or set the "ignore_write_errors" flag in the driver.	Do NOT
	      play with this without grokking the driver source code first.

       -N     Get/set  max  visible  number of sectors, also known as the Host
	      Protected Area setting.  Without a parameter,  -N	 displays  the
	      current  setting,	 which	is  reported  as two values: the first
	      gives the current max sectors setting, and the second shows  the
	      native  (real)  hardware	limit  for  the	 disk.	The difference
	      between these two values indicates how many sectors of the  disk
	      are currently hidden from the operating system, in the form of a
	      Host Protected Area (HPA).  This area is often used by  computer
	      makers  to hold diagnostic software, and/or a copy of the origi-
	      nally provided operating system for recovery purposes.   Another
	      possible	use  is to hide the true capacity of a very large disk
	      from a BIOS/system that cannot normally cope with drives of that
	      size  (eg.  most	current	 {2010}	 BIOSs cannot deal with drives
	      larger than 2TB, so an HPA could be used to cause a 3TB drive to
	      report  itself as a 2TB drive).  To change the current max (VERY
	      DANGEROUS, DATA LOSS IS EXTREMELY LIKELY), a new value should be
	      provided	(in base10) immediately following the -N option.  This
	      value is specified as a count of sectors, rather than  the  "max
	      sector address" of the drive.  Drives have the concept of a tem-
	      porary (volatile) setting which is lost  on  the	next  hardware
	      reset,  as  well	as a more permanent (non-volatile) value which
	      survives resets and power cycles.	 By default, -N	 affects  only
	      the temporary (volatile) setting.	 To change the permanent (non-
	      volatile) value,	prepend	 a  leading  p	character  immediately
	      before  the  first  digit	 of the value.	Drives are supposed to
	      allow only a single permanent change per	session.   A  hardware
	      reset  (or  power cycle) is required before another permanent -N
	      operation can succeed.  Note that any attempt to set this	 value
	      may  fail if the disk is being accessed by other software at the
	      same time.  This is because setting the value requires a pair of
	      back-to-back drive commands, but there is no way to prevent some
	      other command from being inserted between them  by  the  kernel.
	      So if it fails initially, just try again.	 Kernel support for -N
	      is buggy for many adapter types across many kernel versions,  in
	      that  an	incorrect  (too	 small)	 max  size  value is sometimes
	      reported.	 As of the 2.6.27 kernel, this does finally seem to be
	      working on most hardware.

	      Offsets  to given number of GiB (1024*1024*1024) when performing
	      -t timings of device reads.  Speed changes (about	 twice)	 along
	      many  mechanical	drives.	  Usually the maximum is at the begin-
	      ning, but not always.  Solid-state  drives  (SSDs)  should  show
	      similar timings regardless of offset.

       -p     Attempt to reprogram the IDE interface chipset for the specified
	      PIO mode, or attempt to auto-tune for the "best" PIO  mode  sup-
	      ported  by  the  drive.  This feature is supported in the kernel
	      for only a few "known" chipsets, and even then  the  support  is
	      iffy  at	best.	Some  IDE chipsets are unable to alter the PIO
	      mode for a single drive, in which case this option may cause the
	      PIO  mode	 for both drives to be set.  Many IDE chipsets support
	      either fewer or more than the standard six (0 to 5)  PIO	modes,
	      so  the  exact  speed  setting that is actually implemented will
	      vary by chipset/driver sophistication.  Use  with	 extreme  cau-
	      tion!  This feature includes zero protection for the unwary, and
	      an unsuccessful outcome may result in severe filesystem  corrup-

       -P     Set  the	maximum sector count for the drive's internal prefetch
	      mechanism.  Not all drives support  this	feature,  and  it  was
	      dropped from the offical spec as of ATA-4.

	      When  using the SAT (SCSI ATA Translation) protocol, hdparm nor-
	      mally prefers to use the 16-byte command format whenever	possi-
	      ble.   But  some	USB drive enclosures don't work correctly with
	      16-byte commands.	 This option can be used to force use  of  the
	      smaller  12-byte	command	 format with such drives.  hdparm will
	      still revert to 16-byte commands for things that cannot be  done
	      with the 12-byte format (e.g. sector accesses beyond 28-bits).

       -q     Handle  the  next option quietly, suppressing normal output (but
	      not error messages).  This is useful for reducing screen clutter
	      when running from system startup scripts.	 Not applicable to the
	      -i or -v or -t or -T options.

       -Q     Get or set the device's command queue_depth, if supported by the
	      hardware.	  This	only works with 2.6.xx (or later) kernels, and
	      only with device and driver combinations which support  changing
	      the  queue_depth.	  For  SATA  disks, this is the Native Command
	      Queuing (NCQ) queue depth.

       -r     Get/set read-only flag for the device.  When set,	 Linux	disal-
	      lows write operations on the device.

       -R     Get/set  Write-Read-Verify  feature,  if	the drive supports it.
	      Usage: -R0 (disable) or -R1 (enable).  This feature is  intended
	      to have the drive firmware automatically read-back any data that
	      is written by software, to verify that the data was successfully
	      written.	 This  is  generally  overkill, and can slow down disk
	      writes by as much as a factor of two (or more).

	      Reads from the specified sector number, and dumps	 the  contents
	      in  hex  to  standard  output.   The sector number must be given
	      (base10) after this option.  hdparm will issue a low-level  read
	      (completely  bypassing  the  usual block layer read/write mecha-
	      nisms) for the specified sector.	This can be  used  to  defini-
	      tively  check whether a given sector is bad (media error) or not
	      (doing so through the usual mechanisms can sometimes give	 false

	      This is an alias for the --write-sector option.  VERY DANGEROUS.

       -s     Enable/disable  the power-on in standby feature, if supported by
	      the drive.  VERY DANGEROUS.  Do not use  unless  you  are	 abso-
	      lutely  certain  that both the system BIOS (or firmware) and the
	      operating system kernel (Linux >= 2.6.22)	 support  probing  for
	      drives  that  use this feature.  When enabled, the drive is pow-
	      ered-up in the standby mode to allow the controller to  sequence
	      the  spin-up of devices, reducing the instantaneous current draw
	      burden when many drives share a power supply.  Primarily for use
	      in  large RAID setups.  This feature is usually disabled and the
	      drive is powered-up in the active mode  (see  -C	above).	  Note
	      that  a  drive may also allow enabling this feature by a jumper.
	      Some SATA drives support the control of this feature by  pin  11
	      of the SATA power connector. In these cases, this command may be
	      unsupported or may have no effect.

       -S     Put the drive into idle  (low-power)  mode,  and	also  set  the
	      standby (spindown) timeout for the drive.	 This timeout value is
	      used by the drive to determine how long to wait  (with  no  disk
	      activity)	 before	 turning  off the spindle motor to save power.
	      Under such circumstances, the drive may take as long as 30  sec-
	      onds  to respond to a subsequent disk access, though most drives
	      are much quicker.	 The encoding of the timeout value is somewhat
	      peculiar.	  A  value  of zero means "timeouts are disabled": the
	      device will not automatically enter standby mode.	 Values from 1
	      to  240 specify multiples of 5 seconds, yielding timeouts from 5
	      seconds to 20 minutes.  Values from 241 to 251 specify from 1 to
	      11 units of 30 minutes, yielding timeouts from 30 minutes to 5.5
	      hours.  A value of 252 signifies a  timeout  of  21  minutes.  A
	      value  of 253 sets a vendor-defined timeout period between 8 and
	      12 hours, and the value 254 is reserved.	255 is interpreted  as
	      21  minutes  plus	 15  seconds.  Note that some older drives may
	      have very different interpretations of these values.

       -t     Perform timings of device reads  for  benchmark  and  comparison
	      purposes.	  For  meaningful  results,  this  operation should be
	      repeated 2-3 times on an otherwise  inactive  system  (no	 other
	      active  processes)  with	at least a couple of megabytes of free
	      memory.  This displays the speed of reading through  the	buffer
	      cache  to the disk without any prior caching of data.  This mea-
	      surement is an indication of how	fast  the  drive  can  sustain
	      sequential  data reads under Linux, without any filesystem over-
	      head.  To ensure accurate	 measurements,	the  buffer  cache  is
	      flushed during the processing of -t using the BLKFLSBUF ioctl.

       -T     Perform timings of cache reads for benchmark and comparison pur-
	      poses.   For  meaningful	results,  this	operation  should   be
	      repeated	2-3  times  on	an otherwise inactive system (no other
	      active processes) with at least a couple of  megabytes  of  free
	      memory.	This  displays	the speed of reading directly from the
	      Linux buffer cache without disk  access.	 This  measurement  is
	      essentially  an  indication  of the throughput of the processor,
	      cache, and memory of the system under test.

	      For Solid State Drives (SSDs).  EXCEPTIONALLY DANGEROUS. DO  NOT
	      USE  THIS OPTION!!  Tells the drive firmware to discard unneeded
	      data sectors, destroying any data that  may  have	 been  present
	      within  them.   This makes those sectors available for immediate
	      use by the firmware's garbage collection mechanism,  to  improve
	      scheduling  for  wear-leveling  of the flash media.  This option
	      expects one or more sector range	pairs  immediately  after  the
	      option:  an  LBA	starting  address, a colon, and a sector count
	      (max 65535), with no intervening spaces.	EXCEPTIONALLY  DANGER-

	      E.g.  hdparm --trim-sector-ranges 1000:4 7894:16 /dev/sdz

	      Identical	 to  --trim-sector-ranges  above,  except  the list of
	      lba:count pairs is read from stdin rather than  being  specified
	      on  the  command	line.  This can be used to avoid problems with
	      excessively long command lines.  It  also	 permits  batching  of
	      many more sector ranges into single commands to the drive, up to
	      the currently configured transfer limit (max_sectors_kb).

       -u     Get/set the interrupt-unmask flag for the drive.	A setting of 1
	      permits  the driver to unmask other interrupts during processing
	      of a disk interrupt, which greatly improves Linux's  responsive-
	      ness and eliminates "serial port overrun" errors.	 Use this fea-
	      ture with caution: some  drive/controller	 combinations  do  not
	      tolerate	the increased I/O latencies possible when this feature
	      is enabled, resulting in massive filesystem corruption.  In par-
	      ticular, CMD-640B and RZ1000 (E)IDE interfaces can be unreliable
	      (due to a hardware flaw) when this option is  used  with	kernel
	      versions	earlier	 than 2.0.13.  Disabling the IDE prefetch fea-
	      ture of these interfaces (usually a BIOS/CMOS setting)  provides
	      a safe fix for the problem for use with earlier kernels.

       -v     Display some basic settings, similar to -acdgkmur for IDE.  This
	      is also the default behaviour when no options are specified.

       -V     Display program version and exit immediately.

	      Display extra diagnostics from some commands.

       -w     Perform a device reset (DANGEROUS).  Do NOT use this option.  It
	      exists for unlikely situations where a reboot might otherwise be
	      required to get a confused drive back into a useable state.

	      Writes zeros to the specified sector  number.   VERY  DANGEROUS.
	      The  sector  number  must	 be  given (base10) after this option.
	      hdparm will issue a low-level write  (completely	bypassing  the
	      usual  block  layer read/write mechanisms) to the specified sec-
	      tor.  This can be used to force a drive to repair a  bad	sector
	      (media error).

       -W     Get/set the IDE/SATA drive's write-caching feature.

       -X     Set  the IDE transfer mode for (E)IDE/ATA drives.	 This is typi-
	      cally used in combination with -d1 when enabling DMA  to/from  a
	      drive  on	 a supported interface chipset, where -X mdma2 is used
	      to select multiword DMA mode2 transfers and -X sdma1 is used  to
	      select  simple mode 1 DMA transfers.  With systems which support
	      UltraDMA burst timings, -X udma2	is  used  to  select  UltraDMA
	      mode2 transfers (you'll need to prepare the chipset for UltraDMA
	      beforehand).  Apart from that, use of this option is seldom nec-
	      essary since most/all modern IDE drives default to their fastest
	      PIO transfer mode at power-on.  Fiddling with this can  be  both
	      needless	and risky.  On drives which support alternate transfer
	      modes, -X can be used to switch the  mode	 of  the  drive	 only.
	      Prior to changing the transfer mode, the IDE interface should be
	      jumpered or programmed (see -p option) for the new mode  setting
	      to  prevent  loss	 and/or	 corruption  of	 data.	 Use this with
	      extreme caution!	For the PIO (Programmed Input/Output) transfer
	      modes  used  by Linux, this value is simply the desired PIO mode
	      number plus 8.  Thus, a value of 09 sets PIO mode1,  10  enables
	      PIO  mode2,  and	11 selects PIO mode3.  Setting 00 restores the
	      drive's "default" PIO mode, and 01 disables IORDY.   For	multi-
	      word DMA, the value used is the desired DMA mode number plus 32.
	      for UltraDMA, the value is the desired UltraDMA mode number plus

       -y     Force  an	 IDE drive to immediately enter the low power consump-
	      tion standby mode, usually causing it to spin down.  The current
	      power mode status can be checked using the -C option.

       -Y     Force  an	 IDE  drive to immediately enter the lowest power con-
	      sumption sleep mode, causing it to shut down completely.	A hard
	      or soft reset is required before the drive can be accessed again
	      (the Linux IDE driver will automatically handle issuing a	 reset
	      if/when  needed).	  The current power mode status can be checked
	      using the -C option.

       -z     Force a kernel re-read of the partition table of	the  specified

       -Z     Disable  the  automatic power-saving function of certain Seagate
	      drives (ST3xxx models?), to prevent them	from  idling/spinning-
	      down at inconvenient times.

       ATA Security Feature Set

       These  switches	are  DANGEROUS	to experiment with, and might not work
       with some kernels.  USE AT YOUR OWN RISK.

	      Display terse usage info for all of the --security-* options.

	      Freeze the drive's security settings.  The drive does not accept
	      any security commands until next power-on reset.	Use this func-
	      tion in combination with --security-unlock to protect drive from
	      any  attempt to set a new password. Can be used standalone, too.
	      No other options are permitted on the  command  line  with  this

       --security-unlock PWD
	      Unlock  the  drive, using password PWD.  Password is given as an
	      ASCII string and is padded with NULs to  reach  32  bytes.   The
	      applicable  drive	 password  is  selected with the --user-master
	      switch (default is "user" password).  No other options are  per-
	      mitted on the command line with this one.

       --security-set-pass PWD
	      Lock  the	 drive, using password PWD (Set Password) (DANGEROUS).
	      Password is given as an ASCII string and is padded with NULs  to
	      reach  32	 bytes.	 Use the special password NULL to set an empty
	      password.	 The applicable drive password is  selected  with  the
	      --user-master switch (default is "user" password) and the appli-
	      cable security mode with the --security-mode switch.   No	 other
	      options are permitted on the command line with this one.

       --security-disable PWD
	      Disable drive locking, using password PWD.  Password is given as
	      an ASCII string and is padded with NULs to reach 32 bytes.   The
	      applicable  drive	 password  is  selected with the --user-master
	      switch (default is "user" password).  No other options are  per-
	      mitted on the command line with this one.

       --security-erase PWD
	      Erase  (locked) drive, using password PWD (DANGEROUS).  Password
	      is given as an ASCII string and is padded with NULs to reach  32
	      bytes.   Use  the	 special  password  NULL to represent an empty
	      password.	 The applicable drive password is  selected  with  the
	      --user-master  switch  (default  is  "user" password).  No other
	      options are permitted on the command line with this one.

       --security-erase-enhanced PWD
	      Enhanced erase (locked) drive, using password  PWD  (DANGEROUS).
	      Password	is given as an ASCII string and is padded with NULs to
	      reach 32 bytes.  The applicable drive password is selected  with
	      the --user-master switch (default is "user" password).  No other
	      options are permitted on the command line with this one.

       --user-master USER
	      Specifies which password (user/master) to select.	  Defaults  to
	      user  password.	Only  useful  in  combination with --security-
	      unlock,  --security-set-pass,  --security-disable,   --security-
	      erase or --security-erase-enhanced.
		      u	      user password
		      m	      master password

       --security-mode MODE
	      Specifies	 which	security mode (high/maximum) to set.  Defaults
	      to high.	Only useful in combination with --security-set-pass.
		      h	      high security
		      m	      maximum security

	      OWN RISK.


       As  noted  above, the -m sectcount and -u 1 options should be used with
       caution at first, preferably on a read-only  filesystem.	  Most	drives
       work  well with these features, but a few drive/controller combinations
       are not 100% compatible.	 Filesystem  corruption	 may  result.	Backup
       everything before experimenting!

       Some options (e.g. -r for SCSI) may not work with old kernels as neces-
       sary ioctl()'s were not supported.

       Although this utility is intended primarily for use with SATA/IDE  hard
       disk devices, several of the options are also valid (and permitted) for
       use with SCSI hard disk devices and MFM/RLL hard disks with  XT	inter-

       The  Linux  kernel  up until 2.6.12 (and probably later) doesn't handle
       the security unlock and disable commands gracefully and	will  segfault
       and  in	some  cases  even  panic.  The security commands however might
       indeed have been executed by the	 drive.	 This  poor  kernel  behaviour
       makes the PIO data security commands rather useless at the moment.

       Note  that  the	"security  erase" and "security disable" commands have
       been implemented as two consecutive PIO data commands and will not suc-
       ceed  on	 a  locked drive because the second command will not be issued
       after the segfault.  See the code for hints how patch it to work around
       this  problem.  Despite	the segfault it is often still possible to run
       two instances of hdparm consecutively and issue the two necessary  com-
       mands that way.

       hdparm  has  been  written by Mark Lord <mlord@pobox.com>, the original
       primary developer and maintainer of the (E)IDE driver  for  Linux,  and
       current contributer to the libata subsystem, along with suggestions and
       patches from many netfolk.

       The disable Seagate auto-powersaving code is courtesy of Tomi Leppikan-

       Security freeze command by Benjamin Benz, 2005.

       PIO  data  out security commands by Leonard den Ottolander, 2005.  Some
       other parts by Benjamin Benz and others.

       http://www.t13.org/ Technical Committee T13 AT  Attachment  (ATA/ATAPI)

       http://www.serialata.org/ Serial ATA International Organization.

       http://www.compactflash.org/ CompactFlash Association.

Version 9.43			 November 2012			     HDPARM(8)