dmraid: syncing

[Stefan Armbruster]

Hi,

I've got a somewhat broken installation here, affected by LVM over dmraid, 
similar to https://bugs.launchpad.net/ubuntu/+source/dmraid/+bug/129285.

My system is a Intel fakeraid configuration using RAID 1.
/dev/mapper/isw_bedhadgieeh_Volume0 consists of /dev/sda and /dev/sdb. Using 
LVM filtering, I forced the usage of /dev/sda4 as a PV. 

Mountpoints:
/dev/mapper/isw_bedhadgieeh_Volume02 /
/dev/mapper/volgroup-home /home
/dev/mapper/volgroup-var /var
/dev/mapper/volgroup-music /music

In order to solve the LVM trouble, I'd like to remove LVM and create my 
partitions directly on /dev/isw_bedhadgieeh_Volume0. 

My idea is to do the following:
1) mkfs.ext3 /dev/sdb4
2) copy all data from all LVs (/home,/var and /music) to /dev/sdb4

/dev/sda4 (holding LVM) and /dev/sdb4 (ext3) are out of sync now. How could 
this be solved? Would a 'dd if=/dev/sdb4 of=/dev/sda4' suffice?
Or is there a way to tell dmraid to sync or to use a specific disc for read 
operations?
When writing to the dmraid device, the write is effectivly executed on both 
underlying devices (somewhat clear, that's RAID 1). What happens on reads? 
Is /dev/sda or /dev/sdb used?

Is there a way to set a disk manually faulty like in mdadm?

Thanks in advance,
Stefan