Choose "local_dev" option to assign sdb1 as the image home
There are other options, e.g. sshfs, samba or nfs, you can use when network is available. This is very useful when 2nd local disk is not available.
Since we choose "local_dev" option, we can use 2nd disk or USB flash drive to save 1st disk's image. If using USB flash drive as repository, inster USB flash drive and wait a few secs.