by Sachin Sharma, Product Marketing, VMware
Layering in Horizon Mirage is an important concept to understand. The layering technology that is implemented in Horizon Mirage gives IT great flexibility in managing physical and virtual endpoints. We’ll take this opportunity to provide more details on how layering works in Horizon Mirage.
Let’s first take a look at what Horizon Mirage is: a solution for managing physical and virtual endpoints. Horizon Mirage is unique in its offering from an endpoint management stance. IT gets all the benefits of having disaster recovery, image management, and OS/hardware migration capabilities – all built into a unified solution. Physical endpoints, including desktops and laptops, can easily be managed. Centralized virtual endpoints and client-hosted VMs can also be managed. Horizon Mirage also offers unique support for efficient and optimized image delivery over the WAN, hence being able to support campus, branch and remote users.
So how does layering fit in?
Horizon Mirage offers IT the ability to define a base image (referred to as a “base layer”) and a set of application layers (referred to as “app layers”). A base layer consists of the operating system, common software and core applications. An application layer can consist of one or more applications, which are packaged and delivered to endpoints without the need to install them, and without the restrictions or limitations of application virtualization. These layers in Horizon Mirage also offer seamless support to preserve user-installed or third-party PCLM-managed applications. Horizon Mirage layers can be added, removed, updated or enforced just like you’d expect from any other layering technology. Additionally, IT can deliver any apps with kernel drivers, shell plug-ins, etc. Clearly from a functionality and semantics perspective, this layering concept has immense benefits for IT.
There are different methods and techniques to implement layering. For instance, some layering solutions use dynamic in-path composition. Horizon Mirage differs from that type of implementation. Instead, it uses static offline composition. That is, layers are delivered to a staging area at the endpoint while users continue to work, and layers are merged in the background. Upon reboot, the old image is replaced by the newly merged image and the resulting image is a standard Windows image. Static composition has several benefits over dynamic composition. First, it is a standard Windows image, hence fully compatible with any application and system utilities. Second, there is no runtime overhead associated with interception and merging of files and registry keys on the fly. Third, it is a more robust solution as it is not susceptible to dynamic merge-errors.
What about conflicts between layers? Conflicts can sometimes arise when working with multiple layers. For example, driver conflicts between different applications could be an issue. Horizon Mirage combats this by merging the Windows driver store from different layers into a single coherent driver store. Another example is application-layer conflicts. Which layer wins? With Horizon Mirage, the default behavior is for application layers to take precedence over base layers. Application layers also take precedence over user-installed apps, to ensure that IT-managed apps will run correctly at the endpoints. In the exceptional case that an administrator insists on giving preference to user-installed apps (or to user-installed base layers) Horizon Mirage can support that use case as well, via policy definition. For DLL conflicts between layers, Horizon Mirage automatically selects the most recent version of a DLL where multiple copies are present in the layers. Finally, Horizon Mirage also offers a dry-run tool that analyzes the potential conflicts between app, base, and user-installed layers, and produces a “what-if” conflict report before actually applying the updates.
With Horizon Mirage, endpoints are initially centralized to the datacenter. During this process, data objects are maintained in a single-instance store and hence incur fairly small overhead, while still keeping logical copies of the images. An application file is only stored once in the repository, regardless of the number of endpoints using it. By keeping a separate virtual copy, Horizon Mirage offers a great additional capability – cost-effective recovery with quick restore of persistent virtual machines. In the case of virtual machine endpoints, if an ESXi host fails or a storage failure occurs, Horizon Mirage can quickly help restore virtual machines onto new hardware. Recovery across diverse hardware platforms and even different hypervisor platforms such as OpenStack is a key benefit that Horizon Mirage provides – a more flexible recovery option with less ‘lock-in’ than other layering products.
Although not yet supported, Horizon Mirage can be used to update Horizon View desktops. The issue with using Horizon Mirage in this capacity is that the updates are all applied to the desktops at the first available opportunity, which can cause CPU and I/O storms. This can be easily addressed with the introduction of a randomization interval which will enable the updates to be applied without the spike in resource demands. Using Horizon Mirage in this way will update the operating-system layer and IT-managed application layers and allow user-installed applications and user data to be preserved. Horizon Mirage manages Horizon View desktops so that desktops in a pool have identical base layers and application layers. With new storage solutions and technologies rapidly entering the market, significant storage savings can be realized due to storage deduplication. This means the base layer (operating system files and core applications) will only be saved to disk once. The Horizon Mirage approach decouples storage savings from layering and management and enables customers to get the best of everything.
Understanding how layering in Horizon Mirage works is a key component in understanding how the entire solution works. The flexibility and benefits that IT receives with layering is tremendous. For more information on Horizon Mirage, visit the Horizon Mirage product page.
