新内核已经编译完成，并加入ext4，如果使用ext4
[root@kernel ~]# uname -a
Linux kernel 2.6.34 #1 Mon Aug 9 01:58:22 CST 2010 i686 i686 i386 GNU/Linux

事先已经加入了ext4支持，是加入内核，而不是模块，就是怕出问题，现在拿什么工具用啊，我准备了一个LV，单独分区，现在还没有格式化，我的系统里没有mkfs.ext4这个文件
[root@kernel ~]# mkf
mkfifo       mkfontscale  mkfs.cramfs  mkfs.ext3    mkfs.vfat
mkfontdir    mkfs         mkfs.ext2    mkfs.msdos

麻烦高手告知，非常感谢，为了试试EXT4，搞得我翻山越岭重新编译内核。

[root@kernel ~]# ls /dev/LVMGroup/
ftp  LogVol00  LogVol01  LogVol02  LogVol03

ftp这个lv我并没有格式化，是留着给ext4，

[root@kernel ~]# mount -l
/dev/mapper/LVMGroup-LogVol00 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/mapper/LVMGroup-LogVol01 on /usr type ext3 (rw)
/dev/mapper/LVMGroup-LogVol03 on /home type ext3 (rw)
/dev/sda1 on /boot type ext3 (rw) [/boot]
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)

终于搞定了，原来这么简单

[root@kernel ~]# mount -l
/dev/mapper/LVMGroup-LogVol00 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/mapper/LVMGroup-LogVol01 on /usr type ext3 (rw)
/dev/mapper/LVMGroup-LogVol03 on /home type ext3 (rw)
/dev/sda1 on /boot type ext3 (rw) [/boot]
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
/dev/mapper/LVMGroup-ftp on /mnt type ext4 (rw)

ext4 is currently included as a Technology Preview in RHEL 5.3. To use it, update to 5.3 or later, boot into 2.6.18-128.el5 or higher, and yum install e4fsprogs.

The e4fsprogs package is designed to install alongside stock e2fsprogs without overlapping, so some utilities are renamed; for example e4fsck, debuge4fs, e4image, etc. rpm -q e4fsprogs | grep bin will give a good summary of what is included.

The ext4 code in RHEL5.3 does not support delayed allocation, as it is a backport of an older ext4 snapshot (2.7.27). The RHEL5.4 kernel is expected to have an update, based on the 2.6.29 ext4 codebase with several post-2.6.29 fixes.