After snapshot-delete, the qcow2 image file size doesn't decrease, isn't that a waste of disk space? Would someone please tell me how to decrease the file size when snapshot-delete, if that's possible? The image file name of my virtual machine is d0.qcow As follows: [root@test1 ]# virsh list Id Name State ---------------------------------------------------- 32 bfbe8ca8-8579-11e2-844a-001018951f48 running [root@test1 ]# qemu-img info d0.qcow image: d0.qcow file format: qcow2 virtual size: 8.0G (8589934592 bytes) disk size: 3.6G cluster_size: 65536 [root@test1 ]# ls -lh total 3.6G -rw------- 1 qemu qemu 3.6G Apr 12 17:13 d0.qcow drwx------ 2 root root 4.0K Apr 12 17:12 held [root@test1 ]# virsh snapshot-list bfbe8ca8-8579-11e2-844a-001018951f48 Name Creation Time State ------------------------------------------------------------ [root@test1 8]# virsh snapshot-create bfbe8ca8-8579-11e2-844a-001018951f48 Domain snapshot 1365758005 created [root@test1 ]# virsh snapshot-create bfbe8ca8-8579-11e2-844a-001018951f48 Domain snapshot 1365758022 created [root@test1 bfbe8ca8-8579-11e2-844a-001018951f48]# virsh snapshot-list bfbe8ca8-8579-11e2-844a-001018951f48 Name Creation Time State ------------------------------------------------------------ 1365758005 2013-04-12 17:13:25 +0800 running 1365758022 2013-04-12 17:13:42 +0800 running [root@test1 ]# qemu-img info d0.qcow image: d0.qcow file format: qcow2 virtual size: 8.0G (8589934592 bytes) disk size: 3.8G cluster_size: 65536 Snapshot list: ID TAG VM SIZE DATE VM CLOCK 1 1365758005 127M 2013-04-12 17:13:25 00:00:53.141 2 1365758022 127M 2013-04-12 17:13:42 00:01:09.508 [root@test1 ]# ls -lh total 3.9G -rw------- 1 qemu qemu 3.9G Apr 12 17:14 d0.qcow drwx------ 2 root root 4.0K Apr 12 17:12 held [root@test1 ]# virsh snapshot-delete bfbe8ca8-8579-11e2-844a-001018951f48 1365758022 Domain snapshot 1365758022 deleted [root@test1 ]# qemu-img info d0.qcow image: d0.qcow file format: qcow2 virtual size: 8.0G (8589934592 bytes) disk size: 3.8G cluster_size: 65536 Snapshot list: ID TAG VM SIZE DATE VM CLOCK 0 1970-01-01 08:00:00 00:00:00.000 [root@test1 ]# ls -lh total 3.9G -rw------- 1 qemu qemu 3.9G Apr 12 17:14 d0.qcow drwx------ 2 root root 4.0K Apr 12 17:12 held [root@test1 ]# virsh snapshot-delete bfbe8ca8-8579-11e2-844a-001018951f48 1365758005 Domain snapshot 1365758005 deleted [root@test1 ]# qemu-img info d0.qcow image: d0.qcow file format: qcow2 virtual size: 8.0G (8589934592 bytes) disk size: 3.8G cluster_size: 65536 [root@test1 ]# ls -lh total 3.9G -rw------- 1 qemu qemu 3.9G Apr 12 17:14 d0.qcow drwx------ 2 root root 4.0K Apr 12 17:12 held [root@test1 ]# virsh snapshot-create bfbe8ca8-8579-11e2-844a-001018951f48 Domain snapshot 1365758311 created [root@test1 ]# qemu-img info d0.qcow image: d0.qcow file format: qcow2 virtual size: 8.0G (8589934592 bytes) disk size: 3.8G cluster_size: 65536 Snapshot list: ID TAG VM SIZE DATE VM CLOCK 1 1365758311 252M 2013-04-12 17:18:32 00:05:58.136 [root@test1 ]# ls -lh total 3.9G -rw------- 1 qemu qemu 3.9G Apr 12 17:18 d0.qcow drwx------ 2 root root 4.0K Apr 12 17:12 held [root@test1 ]# virsh snapshot-create bfbe8ca8-8579-11e2-844a-001018951f48 Domain snapshot 1365758338 created [root@test1 ]# qemu-img info d0.qcow image: d0.qcow file format: qcow2 virtual size: 8.0G (8589934592 bytes) disk size: 4.1G cluster_size: 65536 Snapshot list: ID TAG VM SIZE DATE VM CLOCK 1 1365758311 252M 2013-04-12 17:18:32 00:05:58.136 2 1365758338 252M 2013-04-12 17:18:58 00:06:24.272 [root@test1 ]# ls -lh total 4.1G -rw------- 1 qemu qemu 4.1G Apr 12 17:19 d0.qcow drwx------ 2 root root 4.0K Apr 12 17:12 held [root@test1 ]# virsh snapshot-list bfbe8ca8-8579-11e2-844a-001018951f48 Name Creation Time State ------------------------------------------------------------ 1365758311 2013-04-12 17:18:31 +0800 running 1365758338 2013-04-12 17:18:58 +0800 running [root@test1 ]# qemu-img info d0.qcow image: d0.qcow file format: qcow2 virtual size: 8.0G (8589934592 bytes) disk size: 4.1G cluster_size: 65536 Snapshot list: ID TAG VM SIZE DATE VM CLOCK 1 1365758311 252M 2013-04-12 17:18:32 00:05:58.136 2 1365758338 252M 2013-04-12 17:18:58 00:06:24.272 [root@test1 ]# virsh snapshot-delete bfbe8ca8-8579-11e2-844a-001018951f48 1365758338 Domain snapshot 1365758338 deleted [root@test1 ]# qemu-img info d0.qcow image: d0.qcow file format: qcow2 virtual size: 8.0G (8589934592 bytes) disk size: 4.1G cluster_size: 65536 Snapshot list: ID TAG VM SIZE DATE VM CLOCK 1 1365758311 252M 2013-04-12 17:18:32 00:05:58.136 [root@test1 ]# ls -lh total 4.1G -rw------- 1 qemu qemu 4.1G Apr 12 17:20 d0.qcow drwx------ 2 root root 4.0K Apr 12 17:12 held [root@test1 ]# virsh snapshot-delete bfbe8ca8-8579-11e2-844a-001018951f48 1365758311 Domain snapshot 1365758311 deleted [root@test1 ]# qemu-img info d0.qcow image: d0.qcow file format: qcow2 virtual size: 8.0G (8589934592 bytes) disk size: 4.1G cluster_size: 65536 [root@test1 ]# ls -lh total 4.1G -rw------- 1 qemu qemu 4.1G Apr 12 17:20 d0.qcow drwx------ 2 root root 4.0K Apr 12 17:12 held [root@test1 ]# virsh snapshot-list bfbe8ca8-8579-11e2-844a-001018951f48 Name Creation Time State 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