Study guide
Technical reference and lesson notes
In Citrix Provisioning, a vDisk acts like the hard drive for a target device. Instead of every machine using its own local operating system disk, the target device can boot from a shared disk image that is streamed from a Citrix Provisioning server or from shared storage. This is one of the core concepts that makes Citrix Provisioning powerful, especially in environments where many machines need to run from the same standardized image. Citrix describes a vDisk as a VHDX-based image with related property files, such as .pvp, and versioning or differencing files such as .avhdx when applicable.
A good way to think about this is a classroom or training lab. Instead of maintaining hundreds of separate computers individually, you can create one master image and stream that image to many target devices. Each device behaves as though it has its own hard drive, but the operating system is actually being delivered from the Citrix Provisioning environment. This allows administrators to standardize the desktop, reduce image sprawl, and make updates in a controlled way.
vDisks can be stored directly on the Citrix Provisioning server or on shared storage, such as SAN or NAS storage. The important requirement is that the Citrix Provisioning servers must be able to access the vDisk files and that there is enough storage available for the base image, associated property files, and any versioning or differencing disks that are created over time.
There are two main access modes for vDisks: Private Image mode and Standard Image mode. Private Image mode is used when a vDisk is assigned to a single target device and that device needs read/write access. This behaves more like a traditional physical or virtual machine disk. It is commonly used when building, maintaining, or updating the image. Standard Image mode is used when the vDisk is shared by multiple target devices. In this mode, the base image is read-only, and changes are redirected to a write cache instead of being written directly back into the base vDisk. Citrix documents these two modes as Private Image for single-device read/write access and Standard Image for multiple-device shared access with write cache options.
For production use, Standard Image mode is usually the goal. This is where Citrix Provisioning becomes especially valuable. You can maintain one clean image and stream it to many machines. When a target device reboots, changes written to the temporary write cache are typically discarded unless a persistent cache or other persistence strategy has been configured. This makes it easier to return devices to a known-good state after every reboot.
Private Image mode still has an important purpose. It is useful when working on the image itself. For example, if you need to install applications, patch the operating system, update the VDA, or make configuration changes to the base image, you would typically work with the vDisk in a mode that allows writes. After the image is updated and validated, it can be placed back into Standard Image mode for shared production use.
The vDisk creation process starts with a master target device. This device is prepared with the operating system, applications, Citrix components, and any required configuration. In a Citrix Virtual Apps and Desktops environment, this might include installing the VDA. In a physical classroom or lab environment, it might simply include the Windows operating system and the required applications for the users or students.
After the master device is prepared, the Citrix Provisioning Imaging Wizard is used to create the vDisk. The wizard connects to the Citrix Provisioning farm, allows the administrator to select the Provisioning server and store, and creates the new vDisk image file. Citrix’s documentation notes that the Imaging Wizard is used to create the virtual disk file and image the master target device.
During the imaging process, you typically provide the Provisioning server name, the store location, the target device information, and the name of the vDisk. You may also choose whether the disk is dynamic or fixed. A dynamic disk grows as data is written, while a fixed disk reserves the full configured size immediately. In many lab or VDI scenarios, dynamic disks are preferred because they can be more storage-efficient, assuming the environment is planned and monitored properly.
Once the image is created, the master device is shut down and then configured to boot from the network or from the assigned vDisk, depending on the boot method being used. The target device is then started again so the administrator can confirm that the device successfully boots from the Citrix Provisioning vDisk. This validation step is important before assigning the image broadly to other devices.
The overall workflow looks like this: build the master image, install the required Citrix Provisioning target device software, run the Imaging Wizard, create the vDisk, shut down the master, adjust the boot method, boot from the vDisk, validate the image, and then switch to the appropriate access mode for the intended use. Once the vDisk is working correctly, it can be assigned to one or more target devices.
The key takeaway is that Citrix Provisioning separates the operating system image from the endpoint. Instead of each device being managed as an independent machine with its own full disk, target devices can stream from a centrally managed vDisk. Private Image mode is used when the disk needs to be updated or maintained by a single device. Standard Image mode is used when the same clean image needs to be shared across many devices. The write cache handles changes during runtime, allowing the base image to remain protected and consistent.
This model is especially useful for environments that need consistency, fast recovery, and centralized image control. Training labs, classrooms, call centers, non-persistent VDI environments, and large standardized desktop deployments can all benefit from this approach. By properly managing vDisks, access modes, write cache placement, and the imaging process, administrators can reduce operational overhead and maintain a cleaner Citrix Provisioning environment.
Citrix References
https://docs.citrix.com/en-us/provisioning/current-release/manage/managing-vdisks.html
https://docs.citrix.com/en-us/provisioning/current-release/install/vdisks-image-wizard.html
https://docs.citrix.com/en-us/provisioning/current-release/install/target-image-prepare.html
https://docs.citrix.com/en-us/provisioning/7-15/managing-vdisks/vdisks-modes-configure.html
https://docs.citrix.com/en-us/provisioning/7-15/managing-vdisks/write-cache.html