楼上的疑问也是我所担心的。

在网上找到一些资料 http://www.linux-ha.org/HaNFS

Make sure you are using a shared disk device, either shared by hardware between your two servers or by DRBD.

Mount your shared device in one of the machines. For example, if the device is /dev/sdb1 and the directory you want to mount to is /data:

mount -t ext3 /dev/sdb1 /data

If the directory you will export is /data/userdata, create it if it is not there yet:

mkdir /data/userdata

Move /var/lib/nfs to your shared disk, make a link (/var/lib/nfs) to it:

mv /var/lib/nfs /data
ln -s /data/nfs /var/lib/nfs

On the other machine, remove the /var/lib/nfs directory and create a link instead:

rm -fr /var/lib/nfs
ln -s /data/nfs /var/lib/nfs

这一步估计可以保证数据写入正确性的问题，

http://www.linux-ha.org/DRBD/NFS
这里还一些资料
Note that auto_failback is off; we should not fail back unless a human has confirmed that the DRBD state is consistent.
We use the Delay script to create a brief pause during failover operations. It was proposed by Jens Dreger in a post at

看来failback需要人手工来做了

我启动DRBD时出现这种错误,楼主知道是什么原因不?
[root@web01 ~]# /etc/init.d/drbd start
Starting DRBD resources:    [ d0 n0 ].
..........
***************************************************************
DRBD's startup script waits for the peer node(s) to appear.
- In case this node was already a degraded cluster before the
   reboot the timeout is 0 seconds. [degr-wfc-timeout]
- If the peer was available before the reboot the timeout will
   expire after 0 seconds. [wfc-timeout]
   (These values are for resource 'r0'; 0 sec -> wait forever)
To abort waiting enter 'yes' [  11]:yes

我第一次使用#drbdadm create-md r0没有问题,第二次把drbd停止,再运行此命令就出现以下错误
[root@web01 ~]# drbdadm create-md r0

Valid meta-data already in place, recreate new?
[need to type 'yes' to confirm] yes

Creating meta data...
initialising activity log
NOT initialized bitmap (256 KB)
New drbd meta data block sucessfully created.

drbdadm create-md r0
这个只要做一次就可以了，是初始化资源用的，如果你第二次做的话相当于格式化了

明白了，谢谢！！！！

顶下先，虽然不甚明白

看帖 回帖 中华美德

正在研究这个东西.

我在执行drbdadm create-md r0的时候出错，提示如下：

Found ext3 filesystem which uses 2048256 kB
current configuration leaves usable 2048156 kB

Device size would be truncated, which
would corrupt data and result in
'access beyond end of device' errors.
You need to either
   * use external meta data (recommended)
   * shrink that filesystem first
   * zero out the device (destroy the filesystem)
Operation refused.

Command 'drbdmeta /dev/drbd1 v08 /dev/sda12 internal create-md' terminated with exit code 40
drbdadm aborting

就是如果设置元数据在分区内部即设置为 internal，提示的三种解决方法我倒是看懂了。第一种将 元数据设置在别的分区，我不想。第二种缩小文件系统，不会 ，第三种 破坏文件系统，也不太会，不过最后用dd命令搞定了。也不知道对不对，反正最后能用。
测试了主备转换什么的都成功了。
这个分区是我装系统的时候划分的，于是就自动格式化成ext3了。不知道有人解决了这个问题吗？赐教一下！

[ 本帖最后由 luoriddr 于 2008-3-17 18:06 编辑 ]