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HDPARM(8) HDPARM(8)
NAME
hdparm - get/set hard disk parameters
SYNOPSIS
hdparm [ flags ] [device] ..
DESCRIPTION
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 latest kernel
source code.
OPTIONS
When no flags are given, -acdgkmnru is assumed.
-a Get/set sector count for filesystem 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. In the current kernel version
(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). Usage: -A0 (disable) or -A1 (enable).
-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 com-
pletely shut down). The -S, -y, -Y, and -Z flags can be used
to manipulate the IDE power modes.
-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 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 dif-
ference, 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 sec-
tors by relocating them to "spare" sectors reserved by the fac-
tory 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 supply 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.
-Istdin
This is a special "no seatbelts" 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.
-Istdout
This option simply dumps the identify data in hex to stdout, in
a format similar to that from /proc/, and suitable for later
use with the -Istdin option.
-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 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/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 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 (eg. 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 removeable disk, since the root par-
tition 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 sys-
tems. 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 settings. Under rare cir-
cumstances, such failures can result in massive filesystem cor-
ruption.
-M Get/set Automatic Acoustic Management (AAM) setting. Most mod-
ern 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 dif-
ferent levels between 128 and 254. THIS FEATURE IS EXPERIMEN-
TAL AND NOT WELL TESTED. USE AT YOUR OWN RISK.
-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 speci-
fied PIO mode, or attempt to auto-tune for the "best" PIO mode
supported by the drive. This feature is supported in the ker-
nel 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 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 cau-
tion! 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, suppressing normal output. This
is useful for reducing screen clutter when running from system
startup scripts. 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) ker-
nels, and only with the few drives that currently support it.
-r Get/set read-only flag for the device. When set, Linux disal-
lows write operations 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 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 dis-
abled": 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 time-
out 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 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. 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.
-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.
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 responsive-
ness 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 unre-
liable (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 set-
ting) provides a safe fix for the problem for use with earlier
kernels.
-U Un-register an IDE interface. Dangerous. The companion for
the -R option. Intended for use with hardware made specifi-
cally for hot-swapping (very rare!). Use with knowledge and
extreme caution as this can easily hang or damage your system.
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 other-
wise 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 undeterminable; 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 sys-
tems 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. Fid-
dling 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 pro-
grammed (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 consump-
tion standby mode, usually causing it to spin down. The cur-
rent power mode status can be checked using the -C flag.
-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 flag.
-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.
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 (eg. -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 (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.
AUTHOR
hdparm has been written by Mark Lord , the primary
developer and maintainer of the (E)IDE driver for Linux, with sugges-
tions from many netfolk.
The disable Seagate auto-powersaving code is courtesy of Tomi Lep-
pikangas(tomilepp@paju.oulu.fi).
SEE ALSO
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 work-
ing draft, revision 2f, July 26, 1994.
AT Attachment with Packet Interface - 5 (ATA/ATAPI-5), T13-1321D work-
ing draft, revision 3, February 29, 2000.
AT Attachment with Packet Interface - 6 (ATA/ATAPI-6), T13-1410D work-
ing draft, revision 3b, February 26, 2002.
Western Digital Enhanced IDE Implementation Guide, by Western Digital
Corporation, revision 5.0, November 10, 1993.
Enhanced Disk Drive Specification, by Phoenix Technologies Ltd., ver-
sion 1.0, January 25, 1994.
Version 5.7 August 2004 HDPARM(8)
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