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Evaluating VDI storage options

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Providing storage for VDI: Shared or SAN?

When you're selecting storage for VDI, consider whether fault tolerance is important and how many advanced features you need.

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Evaluating VDI storage options

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There are lots of options for storage in a VDI environment. Two of the main choices are shared storage and a storage area network, but it all depends on your requirements.

In a virtual desktop infrastructure (VDI) environment, it's important to keep the virtualization host server from becoming a single point of failure. For many organizations, the solution to this problem has always been to store the virtual machines (VMs) on shared storage.

Why it's good to share

The term "shared storage" refers to a storage array that can be connected to multiple host servers simultaneously. That way, if one host server fails, another host can pick up where the failed host left off because both hosts have access to the same storage.

More on storage for VDI

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Calculating storage needs for VDI

Quiz: What do you know about VDI storage and backup?

Although using shared storage for VDI to facilitate VM failover is the accepted way of configuring a fault-tolerant deployment, there are some drawbacks. For starters, shared storage tends to be expensive and the price may keep it from being an option for smaller organizations.

Another problem is that shared storage can be complicated to configure. At the very least, setting it up usually requires knowledge of either iSCSI or Fibre Channel, and more advanced storage knowledge is often necessary. Hence, the technical aspects of shared storage often put the technology out of reach for smaller organizations that lack the expertise required for a shared storage deployment.

This is where the VMware vSphere Storage Appliance comes into play. Contrary to its name, this is not a hardware-based storage appliance like a lot of other VDI storage hardware products. Instead, it is software that creates a virtual storage appliance.

Because it eliminates the need for shared storage, this software is appealing to smaller organizations. It turns leftover local storage on VMware host servers into a virtual shared-storage array. The storage contents are replicated to each host server, thus creating the illusion that shared storage is in use.

While the vSphere Storage Appliance is not true shared storage for VDI, it provides essentially the same benefits. An additional benefit is that it's simple to deploy and configure. VMware boasts that the entire configuration process consists of five mouse clicks and requires no specialized storage hardware.

The SAN option

A powerful -- but costly -- way to provide storage for VDI is with a storage area network (SAN).

Aberdeen LLC's AberSAN ZFS, for instance, is a true SAN. The appliance is rack-mountable, and is designed to coexist with other Aberdeen AberSAN ZFS appliances. As a result, a single rack can accommodate up to a petabyte of raw storage for VDI.

As you would expect from an enterprise-grade SAN solution, AberSAN ZFS supports pools of storage from any combination of storage hardware. Once deployed, the SAN allows the creation of an unlimited number of snapshots and clones, and there's no limit to the maximum file size.

One of the nice things about the AberSAN ZFS with regard to VDI is that the SAN supports inline deduplication. Virtual desktops are often clones of one another, so many system files exist in multiple VMs. Deduplication can significantly reduce the storage footprint for each virtual desktop, making it tremendously beneficial in a VDI environment.

Virtual desktops can also benefit from the thin provisioning feature of the AberSAN ZFS, which allows administrators to provision virtual desktops with plenty of storage space without needing to worry about physical disk space consumption. With thin provisioning, you can allocate space to VMs as a way of providing for growth, but it doesn't consume physical disk space until it is actually needed.

Many SAN solutions on the market support either iSCSI or Fibre Channel. The AberSAN ZFS can be configured as an iSCSI target, but it can also be used with Fibre Channel.

Choosing a storage appliance for VDI means looking carefully at capacity, cost, connectivity and fault tolerance. You'll also need to evaluate your organization's IT know-how to be sure you have the expertise needed to put that storage product in place.

This was first published in March 2013

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