要在redhat 5.5 上使用xfs 文件系统，必须借助centos 5.5 对于版本的一些软件包。比如kmod-xfs,这个软件包是用来添加xfs.ko这个模块，使 5.5内核支持xfs 文件系统。我的内核是自己编译的，所以xfs已经编译在内核中，不需要kmod-xfs 这个软件包。
废话不说了，详细步骤如下，下载需要软件包：
编译：
安装：
就会有 mkfs.xfs fsck.xfs xfsdump xfsrestore 这两个命令
然后格式化硬盘：
mkfs.xfs -f -d agcount=4 -l size=128m -i size=512 /dev/vg_root/lv_www
-i 默认值为 256
-l 的默认值为 10m
agcount 默认自动分配
-l lazy-count=value
This changes the method of logging various persistent counters in the superblock. Under metadata intensive workloads, these counters are updated and logged frequently enough that the superblock updates become a serialisation point in the filesystem. The value can be either 0 or 1.
With lazy-count=1, the superblock is not modified or logged on every change of the persis-tent counters. Instead, enough information is kept in other parts of the filesystem to be able to maintain the persistent counter values without needed to keep them in the superblock. This gives significant improvements in performance on some configurations. The default value is 0 (off) so you must specify lazy-count=1 if you want to make use of this feature.
修改/etc/fstab
nobarrier
Many hardware RAID have a persistent write cache which preserves it across power failure, interface resets, system crashes, etc. Using write barriers in this instance is not recommended and will in fact lower performance. Therefore, it is recommended to turn off the barrier support and mount the filesystem with "nobarrier". But take care about the hard disk write cache, which should be off.
logbufs=value
Set the number of in-memory log buffers. Valid numbers range from 2-8 inclusive. The default value is 8 buffers for filesystems with a blocksize of 64K, 4 buffers for filesystems with a blocksize of 32K, 3 buffers for filesystems with a blocksize of 16K, and 2 buffers for all other configurations. Increasing the number of buffers may increase performance on some workloads at the cost of the memory used for the additional log buffers and their associated control structures.
logbsize=value
Set the size of each in-memory log buffer. Valid sizes are 16384 (16K) and 32768 (32K). The default value for machines with more than 32MB of memory is 32768, machines with less memory use 16384 by default.
参考文档：
http://www.ibm.com/developerworks/cn/linux/filesystem/l-fs10/index.html
http://saplingidea.javaeye.com/blog/636770