[dm-devel] Simulating faulty disk

[Bryn M. Reeves]

On 10/21/2011 04:13 PM, Yathindra wrote:
>  >mount -t ext3 /dev/sdb /mnt
> Copied some data into /mnt
>  >dmsetup create d0 --table="0 `blockdev --getsize /dev/sdb` delay
> /dev/sdb 0 500"
> device-mapper: reload ioctl failed: Invalid argument
> Command failed

You can't create a mapped device on something while it is mounted as 
device-mapper needs to open it exclusively.

> But as seen from above, dmsetup is failing to create a flakey/delay
> device when /dev/sdb
> has a filesystem on top of it. Is there any workaround ?

Set up the file system the way you want it on sdb first. Then unmount it 
and create the device-mapper devices and mount that.

Regards,
Bryn.