Disk type

- dependent
- Independent

VMDKs, by default, are said to be dependent. In other words, when the virtual machine is snapshot’ed, this disk is included in the snapshot.
Independent disks, however, can have different behaviors when the VM is snapshot’ed.

In normal mode, disks are included in snapshots that you take of the virtual machine.
If you do not want data on the disk to be recorded when you take a snapshot of the virtual machine,
configure the disk to be independent.

測試 - dependent

# 沒有任何 snapshot 時

win8.1-flat.vmdk

# take 一個 snapshot 後

win8.1-000001.vmdk    <-- text file
win8.1-000001-delta.vmdk <-- 新的資料寫這裡

# take 2 個 snapshot 時, 會多了 000002

win8.1-000002.vmdk
win8.1-000002-delta.vmdk

* 當 000001 這 snapshot 被 Delete 後, 000002 會食了它的 Data

Independent - Persistent

Disks in persistent mode behave like conventional disks on your physical computer.
All data written to a disk in persistent mode are written permanently to the disk.

no delta file is associated with this disk during a snapshot operation.

每次 snapshot 都會多個

centos6-Snapshot1.vmsn
centos6-Snapshot2.vmsn

不過 revert snapshot 時, Data 仍在

Independent - Nonpersistent

Changes to disks in nonpersistent mode are discarded when you power off or reset the virtual machine.
Changes to the disk are written to and read from a redo log file that is deleted when you power off or reset.

The disk operates normally except that changes to the disk are permanent even if the virtual machine is reverted to a snapshot.