Provided by: hdparm_9.48+ds-1_i386 bug

NAME

       hdparm - get/set SATA/IDE device parameters

SYNOPSIS

       hdparm [options] [device ...]

DESCRIPTION

       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.

OPTIONS

       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
              completely  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-freeze
              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.

       --dco-identify
              Query  and  dump  information  regarding   drive   configuration
              settings  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
              disabled, 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-
              identify will show that the drive is 48_bit capable, but -I will
              not show it, and nor will the drive accept 48_bit commands.

       --dco-restore
              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
              COMMAND.

       --direct
              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.

       --drq-hsm-error
              VERY  DANGEROUS,  DON'T  EVEN THINK ABOUT USING IT.  This option
              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
              immediately 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
              sectors by relocating them to "spare" sectors  reserved  by  the
              factory  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
              operation, 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.

       --fallocate
              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

       --fibmap
              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
              sector  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
              corrupt 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
              preallocated uncommitted extents in ext4/xfs filesystems, unless
              a sync() is done before using this option.

       --fwdownload
              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
              COMMAND.   The --fwdownload-mode3 , --fwdownload-mode3-max , and
              --fwdownload-mode7  variations  on  basic   --fwdownload   allow
              overriding  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
              differ 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
              editions.

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

       --idle-unload
              Issue an ATA IDLE_IMMEDIATE_WITH_UNLOAD command,  to  unload  or
              park  the  heads  and  put  the  drive into a lower power state.
              Usually 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.

       --Istdin
              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.

       --Istdout
              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
              hundreds 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
              possible.   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
              systems).

       -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
              automatically, 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
              feature  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 Digital recommends lower settings of 4 to 8 on
              many of their drives, due tiny (32kB)  drive  buffers  and  non-
              optimized  buffering  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.

       --make-bad-sector
              Deliberately create a bad sector (aka.  "media  error")  on  the
              disk.   EXCEPTIONALLY  DANGEROUS. DO NOT USE THIS OPTION!!  This
              can  be  useful  for  testing  of  device/RAID  error   recovery
              mechanisms.   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
              sector 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
              immediately (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 genuinely 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
              movements 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
              levels  between  128  and  254.  At the moment, most drives only
              support 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 change.

       -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
              originally  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 temporary (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.

       --offset
              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
              beginning,  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
              supported 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
              caution!  This feature includes zero protection for the  unwary,
              and  an  unsuccessful  outcome  may  result in severe filesystem
              corruption!

       -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 official spec as of ATA-4.

       --prefer-ata12
              When using the  SAT  (SCSI  ATA  Translation)  protocol,  hdparm
              normally  prefers  to  use  the  16-byte command format whenever
              possible.  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
              disallows 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).

       --read-sector
              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
              mechanisms) for the specified  sector.   This  can  be  used  to
              definitively  check  whether a given sector is bad (media error)
              or not (doing so through the usual mechanisms can sometimes give
              false positives).

       --repair-sector
              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
              absolutely  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
              powered-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
              seconds  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
              measurement is an indication of how fast the drive  can  sustain
              sequential  data  reads  under  Linux,  without  any  filesystem
              overhead.  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
              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 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.

       --trim-sector-ranges
              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
              DANGEROUS. DO NOT USE THIS OPTION!!

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

       --trim-sector-ranges-stdin
              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
              responsiveness and eliminates "serial port overrun" errors.  Use
              this feature 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  particular,  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  feature  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.

       --verbose
              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.

       --write-sector
              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
              sector.   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
              typically 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
              necessary 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  multiword  DMA,  the  value  used  is  the
              desired DMA mode number plus 32.  for UltraDMA, the value is the
              desired UltraDMA mode number plus 64.

       -y     Force  an  IDE  drive  to  immediately  enter  the   low   power
              consumption  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
              consumption  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
              device(s).

       -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.

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

       --security-freeze
              Freeze the drive´s security settings.  The drive does not accept
              any security commands  until  next  power-on  reset.   Use  this
              function  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 one.

       --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
              permitted 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
              applicable  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
              permitted 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

              THIS  FEATURE  IS  EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR
              OWN RISK.

FILES

       /etc/hdparm.conf

BUGS

       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
       necessary 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
       interfaces.

       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
       succeed 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
       commands that way.

AUTHOR

       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
       Leppikangas(tomilepp@paju.oulu.fi).

       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.

SEE ALSO

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

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

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