'nova delete' causes of slowness by zeroing of instance logical volumes

Issue

• While using lvm for libvirt_images_type, it shows some slowness for deleting instances
• nova.conf has the below for the image type

libvirt_images_type=lvm

• During 'nova delete' operation, it shows lots of 'dd' processes and that takes lots of time to fill the LVM with zero

# ps aux | grep /bin/dd
root      62982  1.8  0.0 106212  1680 ?        D    19:01 0:01 /bin/dd bs=1048576 if=/dev/zero of=/dev/novainstances/instance-000000de_disk seek=0 count=20480 oflag=direct
root      62991  1.9  0.0 106212  1680 ?        D    19:01 0:01 /bin/dd bs=1048576 if=/dev/zero of=/dev/novainstances/instance-000000e1_disk seek=0 count=20480 oflag=direct
root      62998  1.8  0.0 106212  1680 ?        D    19:01 0:01 /bin/dd bs=1048576 if=/dev/zero of=/dev/novainstances/instance-000000d2_disk seek=0 count=20480 oflag=direct
...