Storage Considerations for Virtual Desktops: Key storage capabilities to ensure VDI success

Good morning folks! This is my last post in this three part blog series. In the last two posts, I highlighted the critical success factors for your VDI projects, and introduced a simple storage sizing exercise for your VDI environments. In this post I will review some essential features for your VDI storage that can help mitigate performance challenges while optimizing storage footprint and enabling a simple management and scaling of storage infrastructure.

I mentioned that storage can be a bottleneck in your VDI performance if not carefully designed. Allocating a large number of disks in your VDI storage can help mitigate this risk and meet the high I/O demand placed by the VDI workload on the underlying storage. However this can lead to overprovisioning of storage, introducing cost-inefficiencies in your VDI environment.  Additionally, moving the entire client attached storage to datacenter is also cost prohibitive. The right storage solution for your VDI should help mitigate the performance challenges while minimizing storage footprint, and thus lower costs. In this post, we will explore a few key storage features that are critical to ensure your VDI project success.

Gaining efficiencies with Clones:

To combat the spiraling storage footprint, clones can be the key feature in VDI storage. Clones work by creating a few base or gold images, and clones linked to these base images. VMware Linked Clones use this approach. It is important to design and configure the base images carefully. The base images contain virtual machines comprising of the OS and the applications that the desktop clients need. Depending on your needs, you may want to create multiple base images that satisfy your user needs. Clones linked to these base images are typically very small in size. All virtual desktops read from the base images and any writes are captured in the clones which contain only the delta data. In order to leverage this VMware feature, the underlying storage must support clones. Dell EqualLogic supports clones and can effectively leverage VMware Linked Clones to help reduce your storage needs.

Tiered storage for right-sizing your VDI environment:

In the last post we saw that typically if you design your storage to satisfy your performance needs, you end up with a lot bigger storage footprint than your end users actually need. This of course is an issue, because then your storage becomes too costly and hurts your VDI project ROI. To overcome this challenge, using tiered storage may be the answer.

Tiered storage typically consists of two or more drive types in a single storage pool. All drive types can handle different number of IOPS. Solid State Disk (SSD) drives, for example, can handle an upwards of 5000 IOPS, far higher than any other spinning media can. But with performance comes the price. SSD drives are also quite a lot more expensive compared to SAS or SATA drives and do not provide comparable storage capacity. To achieve a cost-performance balance, it makes sense to combine SSD and SAS or SATA drives.

Dell EqualLogic hybrid arrays are mixed-media multi-tiered arrays featuring SSD and SAS drives in a single enclosure with auto-tiering capabilities. These arrays constantly monitor data access patterns and automatically move the most frequently accesses data (hot data) to the SSD tier while migrating sparingly accessed data to higher capacity SAS drives. These arrays have proven to be extremely efficient in mitigating storage I/O bottleneck while providing adequate capacity. In a VDI environment, during boot, login or log-off storms, these arrays migrate the right data blocks to SSD, helping extract the required I/O performance while providing the capacity necessary for the deployment. Here is a technical report that provides guidance on building a VDI environment with VMware Horizon View and Dell EqualLogic. The paper also demonstrates how these hybrid-arrays mitigate I/O bottleneck in a VDI deployment.

Optimizing performance through storage-hypervisor integration:

Hypervisor technologies have matured quite a bit over the past few years. Virtualization platforms now offer integration points for storage that help enhance performance. Some storage arrays are better integrated with hypervisor or virtualization layer than others. This integration makes a tremendous difference in performance of your VDI environment. Through this integration, the hypervisor can offload certain storage related tasks to the storage arrays, thus substantially minimizing network traffic and host server overheads.

VMware introduced their vStorage APIs for Array Integration (VAAI) with vSphere 4.5. This integration helps offloading of tasks like hardware assisted locking, data-copy and block-zeroing to storage arrays. Tasks such as VM deployments from pre-defined templates benefit substantially from offloading of these functions to storage. Additionally, in a typical VDI environment, many desktop VMs share one volume and simultaneously access information from the shared volume. By utilizing hardware assisted locking, storage administrators can ensure that the entire volume is not locked by a single VM or a single VMware ESX host at a time, and that the performance of shared volumes does not deteriorate. Dell EqualLogic was one of the first storage solutions to incorporate VAAI support into its firmware.

Storage arrays that support multipath I/O can also help improve performance and availability of your VDI deployments. Dell EqualLogic Multipath I/O (MPIO) for VMware integrates with VMware vStorage APIs for Multipathing. It provides fault-tolerant load balancing and helps improve storage performance and scalability while automating multipath configuration.

Storage that helps simplify scaling and management:

I mentioned in my first blog post in this series that a typical VDI deployment starts with a small pilot and is then gradually extended throughout the organization. This means that typically storage is added in phases as the capacity and I/O performance requirements grow. Traditional storage systems impose difficulties while scaling. Dell EqualLogic, on the other hand, is based on virtualized scale-out architecture and helps simplify scaling of capacity and performance. With scale-out architecture, each storage array is equipped with its own controller resources. So as you add more capacity to meet the needs, the controller resources are also linearly added, ensuring simultaneous scaling of capacity and performance. The scale-out architecture also means that the controller resources needed to accommodate future load conditions are not purchased upfront, allowing the IT staff to pay as they grow their storage environment.

As the storage environment grows, it is important to ensure simple management. EqualLogic software features automate numerous tasks involved in storage configuration, management and scaling.

EqualLogic also offers industry-leading integrated management tools. These tools integrate with hypervisor environment to streamline storage provisioning and management. One such example is EqualLogic Virtual Storage Manager (VSM) for VMware. This toolset is installed as a virtual appliance and accessed directly from VMware vCenter or vSphere Web Client user interface. With EqualLogic, all software tools are available to the users at no additional cost with a valid Dell support contract. These tools provide wide ranging functionality from storage management to performance optimization to data protection and disaster mitigation. With these included tools, administrators can substantially simplify storage management. Here is a brief on how EqualLogic optimizes VMware Horizon View based virtual desktop deployments.

EqualLogic PS M4110 blade SAN arrays further simplify the deployments by consolidating storage, compute and networking in a PowerEdge M1000e blade enclosures.  With the blade SAN arrays, it is now possible to build an entire VDI environment in a compact self-contained blade enclosure. The solution can scale within and outside of the blade enclosure as the deployment grows. Here is a brief on utilizing these modular blade arrays for virtual desktop deployments.

Take Away:

In this series I highlighted the critical success factors for your VDI project success and explained how storage plays a key role in enabling this success. I also illustrated one way to size storage for your VDI so it does not become a bottleneck and provides optimal user experience. In this third post I reviewed key storage features to help optimize performance, lower costs and simplify VDI provisioning. Dell EqualLogic family of virtualized iSCSI storage offers the features and capabilities essential to ensure success of your VDI projects. You can find several resources that can help you through your VDI planning at

Wish you good luck with your VDI projects!

About the Author: Vikram Belapurkar