概述
在在验证JBOD启用Write Cache时，服务器强制掉电是否出现文件系统错误，需要先检查JBOD是否启用了Write Cache。故本文介绍查看JBOD Write Policy，至于服务器掉电是否引发文件系统错误的验证，参考我同事的一篇文章。
实践
显示JBOD Write Cache信息
root@node216:~# hdparm -W /dev/sdj
/dev/sdj:
write-caching = 1 (on)
root@node216:~# hdparm -W 0 /dev/sdj
/dev/sdj:
setting drive write-caching to 0 (off)
write-caching = 0 (off)
root@node216:~# hdparm -W 1 /dev/sdj
/dev/sdj:
setting drive write-caching to 1 (on)
write-caching = 1 (on)
root@node216:~#
显示硬盘的相关设置
hdparm /dev/sda
/dev/sda:
IO_support = 0 (default 16-bit)
readonly = 0 (off)
readahead = 256 (on)
geometry = 19457［柱面数］/255［磁头数］/63［扇区数］, sectors = 312581808［总扇区数］, start = 0［起始扇区数］
显示硬盘的柱面、磁头、扇区数
hdparm -g /dev/sda
/dev/sda:
geometry = 19457［柱面数］/255［磁头数］/63［扇区数］, sectors = 312581808［总扇区数］, start = 0［起始扇区数］
测试硬盘的读取速度
hdparm -T /dev/sda
/dev/sda:
Timing cached reads: 4684 MB in 2.00 seconds = 2342.92 MB/sec
测试硬盘缓存的读取速度
hdparm -T /dev/xvda
/dev/xvda:
Timing cached reads: 11154 MB in 1.98 seconds = 5633.44 MB/sec
检测硬盘的电源管理模式
hdparm -C /dev/sda
/dev/sda:
drive state is: standby [省电模式]
查询并设置硬盘多重扇区存取的扇区数，以增进硬盘的存取效率
hdparm -m /dev/sda
hdparm -m #参数值为整数值如8 /dev/sda
附：硬盘坏道修复方法
检查：smartctl -l selftest /dev/sda
卸载：umount /dev/sda*
修复：badblocks /dev/sda
