hdparm 中文man页面-hdparm -w

NAME

hdparm - 获取/设置硬盘参数

总览

hdparm [ -a [扇区数] ] [ -A [0|1] ] [ -c [芯片组模式] ] [ -C ] [ -d [0|1] ] [ -f ] [ -g ] [ -i ] [ -k [0|1] ] [ -K [0|1] ] [ -L [0|1] ] [ -m [扇区数] ] [ -p [0|1|2|3|4|5] ] [ -P [扇区数] ] [ -q ] [ -r [0|1] ] [ -S [超时] ] [ -T ] [ -t ] [ -u [0|1] ] [ -v ] [ -W [0|1] ] [ -X [传输模式] ] [ -y ] [ -Y ] [ -Z ] [设备] ..

描述

hdparm 提供一个实现各种硬盘控制动作的命令行接口,它由内建 Linux IDE/ST-506设备驱动程序支持.要实现这种功能需要Linux 核心版本为1.2.13或更高.在早期的核心下有一些选项可能不能正常工作.另外,一些选项只是为包含了新的IDE设备驱动程序的核心所支持,像2.0.10版或者更高版本的核心.如果hdparm程序是在使用旧的核心文件(在目录usr/include/linux下)的机器上被编译的,这些选项将无法获得.

选项

当未给出标记时, -acdgkmnru 被作为假设值 (除非一个给定的设备是SCSI设备或某种老式 XT型MFM/RLL,在这种情况下 -gr 和 -adgr 分别是默认值).

-a: 为文件系统提前获得/设置扇区号,可以用来改善连续读取大文件时的系统性能,具体方式为提前读取额外的预期中正在运行的任务所需要的数据块.在当前核心版本(2.0.10版)中默认设置为8个扇区(4KB).对于大多数用途,这个值看起来不错,但在一个大多数文件访问行为是随机搜索的系统中,设置一个小一些的值可能效果会更好.当然,很多 IDE驱动器也有一个独立的内建的预读功能,这在很多情况下可以缓解对文件系统预读功能的需求.
-A: 关闭/打开IDE驱动器预读功能(通常默认为打开).
-c: 查询/打开(E)IDE 32-bit I/O 支持.一个数字的参数可以被用来打开/关闭32-bit I/O 支持.当前支持的值包括 0 关闭 32-bit I/O 支持, 1 打开 32-bit 数据传输, 和 3 以一个芯片组要求的特殊的 sync 流程打开 32-bit data 传输. 值 3 几乎对所有的32-bit IDE 芯片组起作用,但导致稍微多一些的系统开销. 注意,32-bit数据传输仅仅用于通过PCI或VLB总线与接口卡的连接; 所有的IDE驱动器通过排线从接口卡获得的连接仅为16-bit.
-C: 检查当前IDE能耗模式状态, 结果将是下面几种之一未知 (驱动器不支持此命令), 活动/闲置 (普通操作), 待机 (低能耗模式,驱动器待机), or 睡眠 (最低能耗模式, 驱动器被完全关闭). 选项 -S, -y, -Y, and -Z 用来操纵能耗模式.
-d: 为驱动器关闭/打开 "using_dma" 标志. 此选项仅对一些支持 DMA并且对于IDE驱动程序来说是已知的驱动器-接口组合 (包括所有被支持的XT接口).特别的,Intel Triton 芯片组能和很多驱动器一起实现总线控制 DMA 操作.(根据实验).使用 -X34 选项与 -d1 选项组合确保驱动器自身是为多字DMA模式2设计的. 使用DMA不一定对吞吐量或系统性能有改进,但很多人信赖它.
-E: 设置光盘驱动器速度.对于一般性操作这不是必须的,因为驱动器将自动地自行选择自己的速度.如果你想要使用它,就在选项后提供一个数字,通常是2或4.
-f: 当设备退出时同步并刷新指针高速缓存.此操作也作为选项 -t 和 -T 定时的一部分被执行
-g: 显示驱动器物理位置(柱面,磁头,扇区),设备的大小(以扇区为单位), 以及相对于驱动器起始的设备偏移量(以扇区为单位).
-h: 显示简要使用信息(帮助).
-i: 显示引导驱动器时获得的识别信息,如果有的话. 这是一种现代IDE驱动器特性,可能不被较老式的设备支持. 返回的数据可能是或不是当前的,这取决于自系统引导后的行为. 然而,当前的复合模式的扇区计数始终被给出. 要获得更多的关于识别信息的详细阐释,请查阅 AT Attachment Interface for Disk Drives (ANSI ASC X3T9.2 working draft, revision 4a, April 19/93).
-I: 直接从驱动器获取识别信息, 并以原始的,未经过修改和更正的形式显示. 否则便与选项 -i 相同.
-k: 获得/设置驱动器 keep_settings_over_reset 标志. 当此标志被设置,驱动程序将在一个软性的重置后保护选项 -dmu (如同在出错恢复流程中完成的那样) 此标志默认值为关 , 以防止可能由与 -dmu 组合设置导致的驱动器重置循环. 选项 -k 应该仅在你确信用一组选定的设置进行正确的系统操作之后被设置. 实际中,校验驱动器能够读/些并且在此过程中没有出错记录(核心消息, 大多数系统上/var/adm/messages中),是测试一个配置(在用-k之前)必须的.
-K: 设置驱动器的 keep_features_over_reset 标志. 此项设置使驱动器在软性重置后保留 -APSWXZ 标志的设置 (如同在出错恢复流程中完成的那样). 并非所有的驱动器都支持此项特性.
-L: 设置驱动器的doorlock标志. 设置为将锁住一些移动式硬驱动器(像 Syquest,ZIP,Jazz..)的门锁机构.设置为一般Linux根据驱动器用法自动维护门锁机构.(当安装一个文件系统时锁住).但在系统关闭时,如果根分区在一个移动式磁盘上, 可能会有麻烦,因为在关闭后根分区仍在处在安装状态(只读). 所以,使用这个命令在根文件系统以只读的方式重新被安装 ,用户可以在关闭后从驱动器中移走磁盘.
-m: 获得/设置驱动器多重扇区I/O的扇区数.设置为 0 关闭这项特性.多重扇区模式(aka IDE Block 模式),是大多数现代硬盘驱动器的一项特性,它允许每次I/O中断传输多个扇区, 而不是通常的一次中断一个.当这项特性被打开时,操作系统处理磁盘I/O的开销降低30-50%.在许多系统上,它也会在任何地方增加5% - 50% 的数据流量大多数驱动器支持最小的设置为2,4,8或,16个(扇区).较大的设置也可能存在,这取决于驱动器.在许多系统上设置为16或32看起来是最理想的. Western Digital在他们的许多驱动器上推荐设置为4或8. 归因于微小的(32kB)磁盘缓冲和非最优化的缓冲算法. 选项 -i 被用来查出一个已安装驱动器支持的最大设置 (在输出中查找 MaxMultSect 值).一些驱动器声称支持多重扇区模式, 但在某些设置下丢失数据.在极少的情况下,这样的失败会导致 严重的文件系统损坏.
-p: 尝试为指定的PIO模式对IDE接口芯片重编程,或者尝试为驱动器支持的最佳的PIO模式进行自动调整.核心中仅针对于一些"知名"的芯片组支持这项特性,甚至这种支持不一定是最好的.一些IDE芯片组不能为一个单一的驱动器改变PIO模式,在这种情况下此选项可能导致PIO 模式的设置影响到两个驱动器.许多IDE芯片组支持少于或多于标准的六个(0到5)PIO模式, 所以实际实现的精确速度设置将由芯片组和驱动器复杂的配合改变. 谨慎使用. 这项特性不包含任何针对不谨慎的保护措施,一个不成功的结果可能导致 严重的文件系统损坏.
-P: 为驱动器的内部预读机制设置最大扇区数. 不是所有的驱动器都支持这项特性.
-q: 安静的操作下一个标志,压制正常输出. 当从/etc/rc.c/rc.local运行时,可用来减轻屏幕混乱程度. 不适用于 -i 或 -v 或 -t 或 -T 标志.
-r: 获得/设置驱动器的只读标志.当被设置时,设备上的写操作被禁止.
-R: 登记一个IDE接口. 危险. 参见 -U 选项获取更多信息.
-S: 设置驱动器待机(低速运转)超时值. 驱动器根据此值决定在关闭主轴电机以节约能耗之前等待多长时间(没有磁盘操作).在这种状态下,驱动器可能需要来响应一个接下来的磁盘访问,虽然大多数驱动器要快很多.超时值的编码有些特别.值0表示"关".值1到240被指定为5秒的倍数, 也就是超时可以从5秒到20分钟.值241到251指定30分钟的1到11倍, 也就是超时可以从30分钟到5.5个小时.值252表示超时21分钟, 253设置一个销售商定义的超时,255表示21分15秒.
-T: 用于以基准测试和比较为目的的缓存读取计时.要得到有意义的结果, 应该在内存不少于2M,系统没有其它活动(没有其它活动的程序) 的条件下,重复操作2-3次.它显示了不存取磁盘直接从Linux缓存读取数据的速度.这项测量实际上标示了被测系统的处理器,缓存和内存的吞吐量. 如果标志 -t 也被指定,那么一个基于 -T 输出结果的修正量将被综合到 -t 操作报告的结果中.
-t: 用于以基准测试和比较为目的的缓存读取计时.要得到有意义的结果, 应该在内存不少于2M,系统没有其它活动(没有其它活动的程序) 的条件下,重复操作2-3次.它显示了不使用预先的数据缓冲从磁盘这项测量标示了Linux下没有任何文件系统开销时磁盘可以支持多快的连续数据读取.为确保测量的精确,缓存在 -t 的过程中通过BLKFLSBUF控制被刷新. 如果标志 -T 也被指定,那么一个基于 -T 数促结果的修正量将被综合到 -t 操作报告的结果中.
-u: 获得/设置驱动器"不屏蔽中断"标志.设置为 1 允许驱动器在磁盘中断处理过程中不屏蔽别的中断, 它极大改善了Linux的响应性能,并排除了"串行端口溢出"错误. 谨慎使用: 一些驱动器/控制器组合不能承受可能是潜在的 I/O 增长, 而导致 严重的文件系统损坏. 特别, CMD-640B 和 RZ1000 (E)IDE 接口可能是 不可靠的 (由于某种硬件缺陷),当在早于 2.0.16 版本的核心下使用此选项时. 关闭这些接口的(通常通过设置BIOS/CMOS) IDE 预读 特性可以安全的解决这个问题.
-U: 注销一个IDE接口. 危险. -R 的对应选项. 是为特别设计用来做热交换的硬件准备的(很罕见!). 使用时要有充分的知识和 非常的谨慎 ,因为它很容易终止或破坏你的系统. hdparm 的源代码包括一个 'contrib' 目录,里面有一些用户捐赠的在一台 ThinkPad 600E的UltraBay上作热交换的记录. 自己去冒险吧.
-v: 显示所有的设置, 除了 -i (像 -acdgkmnru 对于 IDE, -gr 对于 SCSI 或 -adgr 对于 XT). 这也是未指定任何标志时的默认操作.
-W: 关闭/打开 IDE 驱动器的写缓存特性 (通常默认为 OFF ).
-X: 为较新的 (E)IDE/ATA2 驱动器设置 IDE 传输模式 . 特别是当在一个被支持的接口芯片组(像 Intel 430FX Triton) 上打开通向一个驱动器的DMA时与选项 -d1 组合使用,在这里用 -X34 来选择多字 DMA 模式2 传输. 对于支持 UltraDMA burst timings 的系统,用 -X66 来选择 UltraDMA mode2 传输 (你需要在这之前为 UltraDMA 准备好被支持的芯片组). 另外, 几乎没有必要 使用此标志,因为大多数/全部现代 IDE 驱动器默认它们最快的
PIO 传输模式为打开. 所以摆弄它是没有必要的也是冒险的. 在支持 alternate 传输模式的驱动器上, -X 可以被仅用来选择模式. 在改变传输模式之前, 应该为新模式的设置给 IDE 接口跳线或编程(见 -p 标志) 以防止数据的丢失或损坏. 请非常小心地使用它! 对于 Linux 使用的 PIO 传输模式,此值就是要求的 PIO 模式号加 8. 这样, 值 09 设置 PIO mode1, 10 设置 PIO mode2,
11 设置 PIO mode3. 设置为 00 还原驱动器的默认 PIO 模式, 01 关闭 IORDY. 对于多字 DMA, 使用的值时要求的 DMA 模式号加 32. 对于 UltraDMA ,相应的值是要求 UltraDMA 模式号加64.
-y: 迫使一个 IDE 驱动器立即进入低能耗待机模式, 通常使它低速运转. 当前能耗模式状态可以用 -C 标志来检查.
-Y: 迫使一个 IDE 驱动器立即进入最低能耗睡眠模式, 使它完全关闭. 一个来自硬件或软件的重置可以重新唤醒驱动器. ( 如果需要,Linux IDE 驱动器将自动产生一个重置 ).
-Z: 关闭某些 Seagate 驱动器(STxxx 型?)的自动节能功能, 以防止它们在不适当的时候空转或低速运转.

BUGS

像上面提到的, -m 扇区数 和 -u 1 选项尤其要小心使用, 最好在一个只读文件系统上使用. 大多数驱动器和这些特性配合得很好,但有一些驱动器/控制器组合不是100%兼容的.使用可能导致文件系统损坏. 请在实验之前给所有的数据作备份!

某些选项 (例如: -r 对于 SCSI) 可能在旧的核心下因为核心不支持必要的 icctl() 而不能工作.

虽然这个命令只是为使用 (E)IDE 硬盘设备准备的,但有几个选项也能够(允许)用于带有 XT 接口的 SCSI 硬盘设备和 MFM/RLL 硬盘.

作者

hdparm 是由 Mark Lord <mlord@pobox.com>, Linux (E)IDE 驱动程序的主要开发者和维护者编写的,并听取了很多网友的建议.

关闭 Seagate 自动节能的代码是征得
Tomi Leppikangas(tomilepp@paju.oulu.fi)允许使用的.

另见

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.

Western Digital Enhanced IDE Implementation Guide, by Western Digital Corporation, revision 5.0, November 10, 1993.

Enhanced Disk Drive Specification, by Phoenix Technologies Ltd., version 1.0, January 25, 1994.

#p#

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 completely 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 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" sectors 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 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 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 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 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 circumstances, such failures can result in massive filesystem corruption.
-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. THIS FEATURE IS EXPERIMENTAL 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 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 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, 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) kernels, and only with the few drives that currently support it.
-r: Get/set read-only flag for the device. When set, Linux disallows 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 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 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 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. 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 (usually a BIOS/CMOS setting) 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 specifically 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 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 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 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 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 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.

AUTHOR

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

The disable Seagate auto-powersaving code is courtesy of Tomi Leppikangas(tomilepp@paju.oulu.fi).

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