clear the cow cache

# disconnect the COW image

ISCSI use: ietadm --op delete --tid 1 --lun 0
AOE use: ps -ax|grep mapper_name
kill mapper_name process

#suspend dm activity:
dmsetup suspend mapper_name

#clear the cow cache:
dd if=/dev/zero of=/dev/cowloop

#reload the cow table:
echo "0 {master_size} snapshot /dev/cowloop /dev/masterloop p 64" | dmsetup reload mapper_name

#resume dm activity :
dmsetup resume mapper_name

#reconnect the COW image
ISCSI use: ietadm --op new --tid 1 --lun 0 --params Path=/dev/mapper/mapper_name
AOE use: vblade 0 0 eth3 /dev/mapper/mapper_name &