如何打开硬盘的DMA方式
我按照贴子上的方法远行hdparm -d1 /dev/hda无法打开DMA方式显示：setting using_dma to 1 (on)
HDIO_SET_DMA failed:Operation not permitted
using_dma=0(off) :?: 会不会你的hda其实是光驱?
你用fdisk -l看看你的硬盘究竟是哪个盘 确实是hda,光驱是hdc，而且光驱也打不开DMA方式。 你用的是那一个版本的linux？
是不是redhat7。3以前的版本，如果是的话，应该到via的网站下一个补丁，按照它的说明做就可以了。不过要编译内核，有一些麻烦，建议升级到redhat8。0。 我装的是红旗3.2版。请问该如何打开。 如果你的主板是威盛的话,估计得打补丁编译内核了 试一下这个贴子的方法
http://www.linuxfans.org/nuke/modules.php?name=Forums&file=viewtopic&t=5405&start=0&postdays=0&postorder=asc&highlight=DMA 我确实是via主版，而且我也在via网站下载了补丁，readme是英文，但我边查字典边作，但还有几处不明白，希望各位高手指点！我把原文贴出来。
This README file describes how to patch IDE driver source file,
rebuild the Linux kernel, and measure IDE performance.
Step I: Patch the Linux IDE driver source file
1. The Linux kernel including driver source files are all placed in
the directory /usr/src/linux. You have to change your directory
/usr/src in your console.
#cd /usr/src
2. Before patching your Linux IDE source file, you should decompress
your patch file.
#gunzip xxx-patch-xxx-vpide.gz
3. And then you will find a file "xxx-patch-xxx-vpide" in the current
directory. This file is a patchfile that the Linux utility "patch"
can read.
#patch -p0 <xxx-patch-xxx-vpide
Note: Setting parameter -p0 gives the entire file name unmodified.
Step II: Rebuild the Linux kernel
1. Change the current directory to /usr/src/linux
#cd linux
2. Configure the system. The system will ask about driver settings.
#make xconfig
Note: If you are in text mode, try "make menuconfig".
3. The system will pop up a "Linux configuration window" window
with many driver buttons. Find out the button "ATA/IDE/MFM/RLL support"
and press it. Press the button "IDE,ATA and ATAPI Block devices".
The system will pop up another window. Select "VIA82CXXX chipset support".
Note: Pay attention to your CPU type and check if your system
supports multiple processors. If your system is a uni-processor
system, disable the multiprocessor support.
4. Find out the dependencies of source files and the system will
build a new Makefile.
#make dep
5. If you used to build Linux kernel, you should clean old object
files and force building new kernel.
#make clean
6. And you can build a new kernel image.
#make bzImage
7. It is also possible to "make install", if you have lilo installed
to suit your kernel makefile.
8. Then you have to check /etc/lilo.conf to see if the image point
to /boot/vmlinuz. On the other hand, there must be the line
"image=/boot/vmlinuz" in your lilo.conf.
9. Run "lilo" command in your current directory and you will see
the prompt "Added linux *".
10. Reboot Linux system. You will see the boot message shown below
if using the south bridge vt8233a.
"VP_IDE: vt8233a (rev 00) IDE UDMA133 Controller on pci:slot-num"
Step III: Measure IDE performance
Use the "hdparm" utility to test IDE performance. The utility
provides a command line interface to various hard disk ioctls
supported by the device driver. The following options are available
for how to enable/disable DMA, change the UDMA mode, and measure
the data transfer throughput.
1. The parameter -T is essentially to measure the throughput of the
processor, cache, and the memory of the system, -t is to measure
how fast the drive can sustain sequential data reads.
eg: hdparm -tT /dev/hda
2. The parameter -d1 is to enable DMA mode, -d0 is to disable DMA mode.
eg: hdparm -d1 /dev/hdafor enable DMA
hdparm -d0 /dev/hdafor disable DMA
3. The parameter -X is to switch the transfer mode,
16~18 for SDMA 0~2, 32~34 for MDMA 0~2, 64~70 for UDMA 0~6.
eg: hdparm -X70 /dev/hdafor UDMA 6
4. The parameter -i to check the current transfer mode.
我对Step II下的5、6、7、8、9不太明白，请各位高手祥细指点。
先谢谢大家！！！ 上次有位朋友也有这个问题,他也是重新编译内核就搞定的,不过,不推荐在红旗系列上重新编译内核,因为他们的内核是hack过的,但源码里不一定放上hack过的地方,因此,重新编译的内核可能让你失去一些红旗特有的功能
如果有条件的话,建议试试rh8 make clean的意思好像是清理无用的文件，防止把某些文件（过期的）编译进内核，这样会导致内核变大或是出现错误。
make bzImage是建立内核镜像
第8：
就是让系统引导是采用那个内核镜像。我的RH7。3上在make bzImage之后，在/boot目录想会出现vmlinuz等几个文件，是几个连接文件指向你新编译出的内核镜像。原来的内核镜像一般是vmlinuz2.4.18-3 之类的，你需要在你的引导配置文件中，把它改为新的文件。因为我用GRUB，所以只说GRUB了，我建议你新加一个title，这样如果新内核出错的话，你还可以用旧内核启动。具体参见GRUB的配置，在系统安装中刚有这篇帖子。
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