Creating SR. No such device

When adding new storage repository on XenServer 5.5 you get the following error:
Creating SR
No such device

Solutions
Restart all the XenServer host and add the new storage repository again.

Remove XEN host from pool

1. Find the UUID for the host you want to remove.
# xe host-list

2. Remove the host. Use the UUID from step 1, in this example the UUID is xxxx-xxxx-xxxx-xxxx-xxxx
# xe host-forget uuid=xxxx-xxxx-xxxx-xxxx-xxxx