hdparm 命令使用;关闭硬盘 HDD cache; 硬盘读写性能测试；

最新需要使用硬盘做一些测试，需要使用到hdparm工具，并进行了解，并进行简要记录；

hdparm、dd、fio、都是很好的硬盘测试软件；通常使用其对硬盘信息做基本了解；

关闭硬盘写cache用例：

hdparm -w  /dev/sdh # 查看写缓存状态；
hdparm -w  0 /dev/sdh # 关闭cache,保证数据强一致性；放置断电时数据未落盘；
hdparm -w  1 /dev/sdh # 打开

测试磁盘和磁盘缓存读取速度：

查看磁盘信息：
fdisk -l  /dev/sdh
hdparm /dev/sdh
评估磁盘读取速度：
hdparm -t /dev/sdh
评估磁盘缓存读取速度：
hdparm -t /dev/sdh
直接测试硬盘的读性能(绕过内核页缓存)：
hdparm -tt --direct /dev/sdh
顺序写测试：
time -p  bash -c "dd if=/dev/urandom of=./dd.log bs=1m count=50000"
随机写测试：

命令使用方法说明：

hdparm -h

hdparm - get/set hard disk parameters - version v9.43, by mark lord.

usage:  hdparm  [options] [device ...]

options:
 -a   get/set fs readahead
 -a   get/set the drive look-ahead flag (0/1)
 -b   get/set bus state (0 == off, 1 == on, 2 == tristate)
 -b   set advanced power management setting (1-255)
 -c   get/set ide 32-bit io setting
 -c   check drive power mode status
 -d   get/set using_dma flag
 -d   enable/disable drive defect management
 -e   set cd/dvd drive speed
 -f   flush buffer cache for device on exit
 -f   flush drive write cache
 -g   display drive geometry
 -h   display terse usage information
 -h   read temperature from drive (hitachi only)
 -i   display drive identification
 -i   detailed/current information directly from drive
 -j   get/set western digital "idle3" timeout for a wdc "green" drive (dangerous)
 -k   get/set keep_settings_over_reset flag (0/1)
 -k   set drive keep_features_over_reset flag (0/1)
 -l   set drive doorlock (0/1) (removable harddisks only)
 -m   get/set multiple sector count
 -m   get/set acoustic management (0-254, 128: quiet, 254: fast)
 -n   get/set ignore-write-errors flag (0/1)
 -n   get/set max visible number of sectors (hpa) (very dangerous)
 -p   set pio mode on ide interface chipset (0,1,2,3,4,...)
 -p   set drive prefetch count
 -q   change next setting quietly
 -q   get/set dma queue_depth (if supported)
 -r   get/set device readonly flag (dangerous to set)
 -r   get/set device write-read-verify flag
 -s   set power-up in standby flag (0/1) (dangerous)
 -s   set standby (spindown) timeout
 -t   perform device read timings
 -t   perform cache read timings
 -u   get/set unmaskirq flag (0/1)
 -u   obsolete
 -v   use defaults; same as -acdgkmur for ide drives
 -v   display program version and exit immediately
 -w   perform device reset (dangerous)
 -w   get/set drive write-caching flag (0/1)
 -x   obsolete
 -x   set ide xfer mode (dangerous)
 -y   put drive in standby mode
 -y   put drive to sleep
 -z   re-read partition table
 -z   disable seagate auto-powersaving mode
 --dco-freeze      freeze/lock current device configuration until next power cycle
 --dco-identify    read/dump device configuration identify data
 --dco-restore     reset device configuration back to factory defaults
 --direct          use o_direct to bypass page cache for timings
 --drq-hsm-error   crash system with a "stuck drq" error (very dangerous)
 --fallocate       create a file without writing data to disk
 --fibmap          show device extents (and fragmentation) for a file
 --fwdownload            download firmware file to drive (extremely dangerous)
 --fwdownload-mode3      download firmware using min-size segments (extremely dangerous)
 --fwdownload-mode3-max  download firmware using max-size segments (extremely dangerous)
 --fwdownload-mode7      download firmware using a single segment (extremely dangerous)
 --idle-immediate  idle drive immediately
 --idle-unload     idle immediately and unload heads
 --istdin          read identify data from stdin as ascii hex
 --istdout         write identify data to stdout as ascii hex
 --make-bad-sector deliberately corrupt a sector directly on the media (very dangerous)
 --offset          use with -t, to begin timings at given offset (in gib) from start of drive
 --prefer-ata12    use 12-byte (instead of 16-byte) sat commands when possible
 --read-sector     read and dump (in hex) a sector directly from the media
 --repair-sector   alias for the --write-sector option (very dangerous)
 --security-help   display help for ata security commands
 --trim-sector-ranges        tell ssd firmware to discard unneeded data sectors: lba:count ..
 --trim-sector-ranges-stdin  same as above, but reads lba:count pairs from stdin
 --verbose         display extra diagnostics from some commands
 --write-sector    repair/overwrite a (possibly bad) sector directly on the media (very dangerous)

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