Previously we have familiar to attach disk image to KVM virtual machine in the post "http://techies-world.com/how-to-attach-disk-image-to-kvm-virtual-machine-with-virsh/".
Here its explaining the command to detach disk from KVM virtual machine with virsh.
To achieve this we can use the following command.
#virsh detach-disk server.example.com /dev/vdb --persistent (or --config)
Note to replace "server.example.com" and "/dev/vdb" with appropriate values.