[Users] Deleting a snapshot of eight disks took more than fifteen minutes

Is it reasonable? I created snapshot1 and snapshot2 for the eight disks and then tried to delete snapshot2. And it took 15+ minutes to finish the operation. Here is the disk list: my-vm1_Disk1 40 GB 3 GB data Thin Provision VirtIO OK 2012-Jun-27, 13:24:01 my-vm1_Disk2 10 GB 10 GB data Preallocated VirtIO OK 2012-Jun-25, 23:19:00 my-vm1_Disk3 4 GB < 1 GB data Thin Provision VirtIO OK 2012-Jun-26, 23:27:40 my-vm1_Disk4 3 GB 3 GB data Thin Provision VirtIO OK 2012-Jun-27, 13:24:01 my-vm1_Disk5 3 GB 3 GB data Thin Provision VirtIO OK 2012-Jun-27, 13:24:01 my-vm1_Disk6 4 GB 4 GB data Thin Provision VirtIO OK 2012-Jun-27, 13:24:02 my-vm1_Disk7 5 GB 5 GB data Thin Provision VirtIO OK 2012-Jun-27, 13:24:02 my-vm1_Disk8 6 GB 6 GB data Thin Provision VirtIO OK 2012-Jun-27, 13:24:02 -- Shu Ming <shuming(a)linux.vnet.ibm.com&gt; IBM China Systems and Technology Laboratory