- Standard Image – Select this mode if a vDisk is shared by multiple target devices (write-cache options enabled).
- Private Image – Select this mode if a vDisk is only used by a single target device (read/write access is enabled).
Standard Image mode
Standard Image mode allows multiple target devices to stream from a single vDisk image at the same time. This reduces the amount of vDisk management and reduces storage requirements.
When a vDisk is configured to use Standard Image mode, it is set to read-only mode. Each target device then builds a write cache to store any writes the operating system needs to make. There are several write-cache options available. Because the vDisk is read-only, each time a target device boots, it always boots from a ‘clean’ vDisk. If a machine becomes infected with a virus or spyware, the target device only needs to reboot the image.
When updates are made to a vDisk in Standard Image mode, changes against the base vDisk image are captured in a differencing disk file (.avhdx), resulting in a new version of the base image. Each new version remains directly associated with the base image. Versioning allows for the updates captured in the differencing disk to be staged (Maintenance, Test, Production) before those changes become available to Production devices. If issues are encountered with a version, that version can simply be reverted.
Although each target device uses the same vDisk, Provisioning Services personalizes the streamed image for each target device, providing the information needed to ensure the device is uniquely identifiable on the network. You can also specify additional personality settings for each device: you can store application-specific values in the database and retrieve the target device’s unique value as the device loads.
Private Image mode
The following illustrates Private Image vDisks (read/write) that are each assigned to a single production device, and a Standard Image vDisk (read-only) that is assigned to and shared by a collection of production devices. For Standard Image vDisks, write cache options include cache on server disk, on a device’s hard disk drive, or in the device’s RAM.
- On the Console, right-click on the vDisk for which you want to configure the vDisk access mode, then select vDisk Properties. The vDisk Properties dialog appears.
- Click on the General tab, then select the image mode (Standard or Private) that applies to this vDisk from the Access Mode drop-down list.
- If Standard image was selected, from the cache destination drop-down list, select the appropriate write cache destination.
- Click OK to exit the vDisk Properties dialog.