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HDPARM(8)										HDPARM(8)

       hdparm - get/set hard disk parameters

       hdparm [ flags ] [device] ..

       hdparm  provides  a  command  line  interface to various hard disk ioctls supported by the
       stock Linux ATA/IDE device driver subsystem.  Some options may work  correctly  only  with
       the latest kernels.  For best results, compile hdparm with the include files from the lat-
       est kernel source code.

       When no flags are given, -acdgkmnru is assumed.

       -a     Get/set sector count for filesystem read-ahead.  This is used  to  improve  perfor-
	      mance  in  sequential  reads  of	large  files, by prefetching additional blocks in
	      anticipation of them being needed by the running task.  In the current kernel  ver-
	      sion (2.0.10) this has a default setting of 8 sectors (4KB).  This value seems good
	      for most purposes, but in a system where most file accesses  are	random	seeks,	a
	      smaller  setting might provide better performance.  Also, many IDE drives also have
	      a separate built-in read-ahead function, which alleviates the need for a filesystem
	      read-ahead in many situations.

       -A     Disable/enable the IDE drive's read-lookahead feature (usually ON by default).

       -b     Get/set bus state.

       -B     Set  Advanced Power Management feature, if the drive supports it. A low value means
	      aggressive power management and a high value means better performance. A	value  of
	      255 will disable apm on the drive.

       -c     Query/enable  (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 flags can be used to manipulate the IDE power

       -d     Disable/enable 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 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 cor-
	      rect 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.

       -D     Enable/disable the on-drive defect management feature, whereby the  drive  firmware
	      tries  to automatically manage defective sectors by relocating them to "spare" sec-
	      tors reserved by the factory for such.

       -E     Set cdrom 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 sup-
	      ply a speed number after the option, usually a number like 2 or 4.

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

       -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).

       -i     Display  the  identification info that was obtained from the drive at boot time, if
	      available.  This is a feature of modern IDE drives, and may  not	be  supported  by
	      older  devices.  The data returned may or may not be current, depending on activity
	      since booting the system.  However, the  current	multiple  sector  mode	count  is
	      always shown.  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).

       -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  flag.   There
	      is  a special "no seatbelts" variation on this option, -Istdin which cannot be com-
	      bined with any other options, and 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".
	      This  variation is designed for use with "libraries" of drive identification infor-
	      mation, and can also be used on ATAPI drives which may give media errors	with  the
	      standard mechanism.

       -k     Get/set  the  keep_settings_over_reset  flag for the drive.  When this flag is set,
	      the driver will preserve the -dmu options over a soft reset, (as	done  during  the
	      error  recovery sequence).  This flag defaults to off, to prevent drive reset loops
	      which could be caused by combinations of -dmu settings.  The -k flag should  there-
	      fore 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  neces-
	      sary 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/adm/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  recov-
	      ery sequence).  Not all drives support this feature.

       -L     Set  the	drive's  doorlock  flag.  Setting this to will lock the door mechanism of
	      some removeable hard drives (eg. Syquest, ZIP, Jazz..), and setting it to 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 removeable disk, since the root partition is left mounted
	      (read-only) after shutdown.  So, by using this command to unlock the door 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 mod-
	      ern 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  sys-
	      tems,  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 multi-
	      ple 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 flag 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 set-
	      tings.  Under rare circumstances, such failures can result  in  massive  filesystem

       -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 ownly two lev-
	      els  (quiet  /  fast),  while others may have different levels between 128 and 254.

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

       -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 sup-
	      port is iffy at best.  Some IDE chipsets are unable to alter the	PIO  mode  for	a
	      single  drive, in which case this flag 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.

       -q     Handle  the next flag quietly, supressing normal output.	This is useful for reduc-
	      ing screen clutter when running from /etc/rc.c/rc.local.	Not applicable to the  -i
	      or -v or -t or -T flags.

       -Q     Set  tagged  queue depth (1 or greater), or turn tagged queuing off (0).	This only
	      works with the newer 2.5.xx (or later) kernels, and only with the few  drives  that
	      currently support it.

       -r     Get/set read-only flag for device.  When set, write operations are not permitted on
	      the device.

       -R     Register an IDE interface.  Dangerous.  See the -U option for more information.

       -S     Set the standby (spindown) timeout for the drive.  This value is used by the  drive
	      to  determine how long to wait (with no disk activity) before turning off the spin-
	      dle 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  "off".   Values  from  1 to 240 specify multiples of 5 seconds, for timeouts
	      from 5 seconds to 20 minutes.  Values from 241 to 251 specify from 1 to 11 units of
	      30  minutes, for timeouts from 30 minutes to 5.5 hours.  A value of 252 signifies a
	      timeout of 21 minutes, 253 sets a vendor-defined timeout, and 255 is interpreted as
	      21 minutes plus 15 seconds.

       -T     Perform timings of cache reads for benchmark and comparison purposes.  For meaning-
	      ful 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 mem-
	      ory.  This displays the speed of reading directly from the Linux buffer cache with-
	      out  disk  access.  This measurement is essentially an indication of the throughput
	      of the processor, cache, and memory of the system under test.  If the  -t  flag  is
	      also  specified, then a correction factor based on the outcome of -T will be incor-
	      porated into the result reported for the -t operation.

       -t     Perform timings of device reads for benchmark and comparison purposes.   For  mean-
	      ingful  results,	this operation should be repeated 2-3 times on an otherwise inac-
	      tive 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 measurments, the buffer cache is flushed  during  the
	      processing of -t using the BLKFLSBUF ioctl.  If the -T flag is also specified, then
	      a correction factor based on the outcome of -T will be incorporated into the result
	      reported for the -t operation.

       -u     Get/set  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  (usu-
	      ally  a BIOS/CMOS setting) provides a safe fix for the problem for use with earlier

       -U     Un-register an IDE  interface.   Dangerous.   The  companion  for  the  -R  option.
	      Intended	for  use  with	hardware made specifically for hot-swapping (very rare!).
	      Use with knowledge and extreme caution as this can easily hang or damage your  sys-
	      tem.  The hdparm source distribution includes a 'contrib' directory with some user-
	      donated scripts for hot-swapping on the UltraBay of a ThinkPad 600E.  Use  at  your
	      own risk.

       -v     Display  all settings, except -i (same as -acdgkmnru for IDE, -gr for SCSI or -adgr
	      for XT).	This is also the default behaviour when no flags are specified.

       -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.

       -W     Disable/enable the IDE drive's write-caching feature  (default  state  is  undeter-
	      minable; manufacturer/model specific).

       -x     Tristate device for hotswap (DANGEROUS).

       -X     Set  the	IDE transfer mode for newer (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
	      flag  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 flag) 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 flag.

       -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

       -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 mod-
	      els?), to prevent them from idling/spinning-down at inconvenient times.

       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  (eg. -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 (E)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.

       hdparm has been written by Mark Lord <mlord@pobox.com>, the primary  developer  and  main-
       tainer of the (E)IDE driver for Linux, with suggestions from many netfolk.

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

       AT Attachment Interface for Disk Drives, ANSI ASC X3T9.2 working draft, revision 4a, April
       19, 1993.

       AT  Attachment  Interface with Extensions (ATA-2), ANSI ASC X3T9.2 working draft, revision
       2f, July 26, 1994.

       AT Attachment with Packet Interface - 5 (ATA/ATAPI-5), T13-1321D working  draft,  revision
       3, February 29, 2000.

       AT  Attachment  with Packet Interface - 6 (ATA/ATAPI-6), T13-1410D working draft, revision
       3b, February 26, 2002.

       Western Digital Enhanced IDE Implementation Guide, by Western Digital  Corporation,  revi-
       sion 5.0, November 10, 1993.

       Enhanced  Disk Drive Specification, by Phoenix Technologies Ltd., version 1.0, January 25,

Version 5.2				     May 2002					HDPARM(8)
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