[root@LFS ~]#mount -t reiserfs /dev/raid_lvm/lv_data /mnt/data
About chunk-size :
The chunk-size deserves an explanation. You can never write completely parallel to a set of disks. If you had two disks and wanted to write a byte, you would have to write four bits on each disk, actually, every second bit would go to disk 0 and the others to disk 1. Hardware just doesn't support that. Instead, we choose some chunk-size, which we define as the smallest "atomic" mass of data that can be written to the devices. A write of 16 kB with a chunk size of 4 kB, will cause the first and the third 4 kB chunks to be written to the first disk, and the second and fourth chunks to be written to the second disk, in the RAID-0 case with two disks. Thus, for large writes, you may see lower overhead by having fairly large chunks, whereas arrays that are primarily holding small files may benefit more from a smaller chunk size.
Chunk sizes must be specified for all RAID levels, including linear mode. However, the chunk-size does not make any difference for linear mode.
For optimal performance, you should experiment with the value, as well as with the block-size of the filesystem you put on the array.
The argument to the chunk-size option in /etc/raidtab specifies the chunk-size in kilobytes. So "4" means "4 kB".补充几个问题：
Q:如何得知当前内核是否支持RAID?
A:cat /proc/mdstat 有输出信息则表示内核已支持
或dmesg |grep -i raid dmesg |grep -i md 都能够看到。
Q:如何得知当前内核支持哪几种RAID?
A:安装当前内核源码包，将当前内核配置文档cp到内核源码目录下
cp /boot/config-xxx /usr/src/linux && make menuconfig
看看Device Drivers --->Multi-device support (RAID and LVM)这里的选项就知道了。
或cat /lib/modules/`uname -r`/modules.alias |grep raid0
raid0为查看的级别:raid1,raid5...
假如有输出则表示内核已支持，并且/必须是做为模块加载的。
Q:raidtool和mdadm应该使用哪个？哪里有下载？
A:mdadm可能更方便一些。mdadm和raidtool的区别：
The key differences between mdadm and raidtools are:
mdadm is a single program and not a collection of programs.
mdadm can perform (almost) all of its functions without having
a configuration file and does not use one by default. Also
mdadm helps with management of the configuration file.
mdadm can provide information about your arrays (through
Query, Detail, and Examine) that raidtools cannot.
mdadm does not use /etc/raidtab, the raidtools configuration file,
at all. It has a different configuration file with a different
format and an different purpose.
另外我看的这本书里,讲解的是raidtool，这是在RHEL3中所使用的，但是我在RHEL4中做这个lab
发现四张盘里没有raidtool,只有mdadm，看来RH也是偏向于使用mdadm的 :)
下载地址：
mdadm：
http://www.cse.unsw.edu.au/~neilb/source/mdadm/RPM/
http://www.cse.unsw.edu.au/~neilb/source/mdadm/
raidtool:
ftp://194.199.20.114/linux/fedora/core/2/i386/os/Fedora/RPMS/raidtools-1.00.3-8.i386.rpm
OK,这个lab完成啦。
有机会一定要在真实硬盘上试试raid-0 lvm reiserfs，看看是什么感觉 ^_^
