Physical vs. virtual backup appliances: Make the best choice

The basics remain the same

In a physical vs. virtual decision, companies must correctly size the appliance, regardless of the choice. To do so, they need to collect key data points about their environment that minimally include:

• amount of data to protect;
• applications hosted by cloud service providers (CSPs);
• existing backup software;
• length of backup data retention;
• number of backup streams;
• recovery point objectives;
• recovery time objectives;
• types of applications and data to protect; and
• use of direct-attached storage (DAS) devices, such as tape libraries.

Some of these factors could dictate when companies use a physical or virtual appliance. For instance, if companies host data with a CSP, a virtual appliance may be their only option. Alternatively, if they need a backup appliance that can connect to and manage a tape library, they should deploy a physical backup appliance.

Absent a deciding factor such as one of these, companies will find they have more freedom than ever before to choose between physical and virtual backup appliances.

Physical vs. virtual in remote and branch offices

Conventional wisdom holds that a fully virtualized remote or branch office should use a virtual backup appliance. Companies can easily deploy virtual appliances, centrally manage them, replicate backup data to the central office and avoid new hardware. This logic no longer always applies. Physical backup appliances can have a place in these sized offices when either of the following two criteria hold true:

1. Undersized physical machine in production. Virtual backup appliances will consume additional capacity and performance resources on the physical machine. If the production physical machine already struggles with its current workloads, introducing a new virtual backup appliance will add to its overhead and may negatively impact production virtual machines (VMs). A physical backup appliance keeps backup workloads off the production physical machine.
2. A secondary physical machine to host recoveries. If the production physical machine experiences a hardware failure, the office may have no secondary physical machine available to recover its VMs. Selecting a physical backup appliance that can function as a standby physical machine and host recoveries solves this dilemma.

These two factors help explain why providers such as Unitrends offer physical backup appliances in small form factors, as well as virtual backup appliances, to give companies a choice.

Prepping for the virtual data center

With the rise of software-defined data centers and cloud-first philosophies, virtual backup appliances stand poised to replace a traditional stronghold of physical backup hardware.

Conventional wisdom also holds that companies should use physical backup appliances in their enterprise data centers. These companies often know:

• the amount of data they protect;
• the number of concurrent backup streams run nightly; and
• their forecasted data growth.

Having this knowledge enables them to more confidently acquire dedicated hardware to handle these workloads. But with the rise of software-defined data centers and cloud-first philosophies, virtual appliances stand poised to replace this traditional stronghold of physical backup hardware.

Companies should start with virtual backup appliances in test environments, especially for those companies implementing a cloud-first strategy in their data centers. They can deploy virtual appliances from providers such as HYCU, Unitrends and Veritas in these virtualized environments to ascertain how well they perform before rolling them out into production.

Companies can have a high degree of confidence these virtual backup appliances will handle these workloads. Veritas already internally develops most of its physical NetBackup hardware as virtual appliances. Once it completes testing, Veritas productizes this development and makes development virtual appliances available as its physical NetBackup 5230 and 5340 backup appliances. While the maximum capacity of its virtual NetBackup tops out at 250 TB, Veritas anticipates that limit will rise as more companies adopt virtual appliances in their production data centers.

Verify the virtual appliance has cut the DAS cord

One major feature that companies should assess prior to adopting any virtual backup appliance is its support for cloud-based object storage as a primary storage target. While all enterprise providers of these appliances support cloud-based object storage as an optional storage target, some can still require storage to present itself as an internally attached device to the backup software running on the virtual backup appliance.

General-purpose CSPs, such as AWS, help to meet this requirement. AWS makes its Elastic Block Store (EBS) available to all VMs, backup appliances or otherwise. On the surface, using EBS to store backup data may not seem like a problem since EBS Cold HDD storage volumes cost about the same per gigabyte as the Amazon S3 Standard storage offering.

The problem emerges over time. As companies store more backup data on the AWS EBS storage internally attached to the virtual backup appliance, AWS EBS does not give companies the same flexibility to tier backup data as Amazon S3 does. By using Amazon S3 Standard as the primary backup target -- as virtual backup appliances from HYCU can do -- companies can configure S3 to move backup data to lower-cost tiers of Amazon S3 storage, such as Glacier, as the backups age. Glacier is currently about one-fifth the cost of Amazon S3 Standard storage and can, over time, save companies substantially on their total storage costs.