As server virtualisation has become the norm, we have seen the emergence of the virtual backup appliance.
Virtual environments enable the creation of “soft’ servers,” allowing multiple operating systems that reside in physical machines to run their own apps. It’s this capability that the virtual backup appliance exploits, offering an OS and backup product in a ready-to-use package in a virtual server environment.
Virtual backup appliances are easy to deploy, scalable and often free. And they can offer performance advantages over a backup app on a physical server. But just how robust are they, are they suited to all target media, and just how do you manage them?
In this article we examine the virtual backup appliance as well as its benefits and potential pitfalls.
Virtual appliance: A definition
It’s worth taking a moment to look at the concept of virtual appliances in general. The term “virtual appliance” generally refers to the packaging of an operating system image and application for deployment on a virtualisation platform such as VMware, Microsoft Hyper-V or Citrix XenServer.
Virtual appliances are designed to be deployed with minimal configuration work, which usually consists of answering a set of scripted responses on power-up of the appliance in a virtual guest.
The Open Virtualisation Format (OVF) is an open standard used to deploy applications as virtual appliances and has been available since 2008. OVF is used for virtual appliances in VMware, and there are hundreds of virtual appliances available for download from the company’s website.
Although Microsoft supported the development of OVF, Hyper-V has taken a slightly different route and supports appliances supplied as VHDs (virtual hard disks).
Using an appliance for backup
Today many vendors provide appliances that are based on their existing backup products. Zmanda, for example, offers a virtual backup appliance that is based on its Amanda Enterprise Edition product. Arkeia has a virtual backup appliance that supports small environments and is free to use. There are also appliances available from PHD Virtual Technologies, Symantec (NetBackup PureDisk Virtual Appliance), FalconStor (Virtual Tape Library and Continuous Data Protector Virtual Appliance) and EMC/Avamar.
Appliances have been pre-built by the vendor to include all the required components of an application at a specific supported level of configuration, so minimal additional work is required to make an appliance operational after boot-up.
This “power up, configure and go” approach contrasts with a standard deployment, where an operating system is built and patched to local standards before the backup application is deployed. Appliance deployment is therefore quicker and easier than building and deploying a backup application from scratch.
With virtual appliances the process is even simpler than deployment of a hardware appliance; VMware’s vCenter and vSphere client, for example, have a wizard (found under the File menu) that guides users through OVF virtual appliance deployment, prompting for details such as the guest name and target data store.
The source OVF file can reside on a network share, local disk or even be accessed over the Internet. An extra bonus with virtualisation is the ability to easily destroy and re-create an appliance if the configuration is incorrect or mistakes were made answering the deployment script.
A virtual backup appliance also has two other advantages. Firstly, the operating system can be optimised to be automatically deployed with only the components required to run the backup software. This has the benefit of reducing complexity and dependencies in the deployment and reducing use of system resources. The vendor can also harden the deployment, locking down unnecessary features, a task that the server or storage administrator would otherwise have to do.
Benefits of virtual backup appliances
There are a number of additional benefits to be gained from using virtual appliances for backup; note that some of these benefits would also apply to backup applications deployed into standard virtualised operating systems.
- Network performance. Within a virtual infrastructure, networking is implemented as either a virtual VLAN (vSwitch in VMware) or virtual network (Hyper-V), which can exist within one or multiple hypervisors. If communications within the virtual network don’t leave a single hypervisor on a single physical machine, they will benefit from reduced latency, which translates directly into higher throughput of backup data. Backup security can be improved by creating a virtual network purely for backup and keeping it within the hypervisor.
- Scalability. As virtual environments are deployed, virtual backup can be built into the deployment model. This allows backup infrastructure to scale to meet virtual server requirements.
- Speed. Deploying traditional backup infrastructures can be time-consuming. Virtual appliances speed up that process considerably, benefiting from being virtually deployed and preconfigured.
- Integration. Some virtual backup appliances integrate directly into the VMware ESX console, providing consolidated management of a virtual environment. This is particularly useful for the restore process, where data can more easily be restored back to a target guest.
- Compatibility. Most appliances use existing backup products. This reduces training time for staff already familiar with those tools. In addition, features such as backup replication can be achieved between physical and virtual deployments. This is useful, for example, where a virtual backup solution is deployed in a branch office and backups are replicated to a core location.
- Cost. Many backup appliances are free; assuming support isn’t an issue (for example with development environments), a free appliance could be an attractive solution.
Unfortunately, there’s no such thing as a free lunch, and consequently there are trade-offs in using virtual backup appliance solutions.
- Performance. In large-scale deployments, backup performance can be critical. Clearly, a backup application deployed on dedicated hardware will perform better than a virtual backup appliance.
- Device support. Virtual environments may not directly support tape, offering only disk-to-disk backups. This may represent a problem for moving data off-site.
- Upgrade/support. Although virtual appliances are easy to deploy, they still require upgrades and maintenance. This means applying patches as required and upgrading the underlying operating system and backup software. This process could be an issue if the appliance is built on a platform for which there are no in-house skills. The obvious answer would be to transition to a new appliance running later code. This may not always be possible to achieve easily; backups are notoriously difficult to migrate between backup servers and certainly between different versions of the application.
- Sprawl. In large environments it may be necessary to deploy many backup appliances. In this instance the additional management overhead may be an issue.
Virtual appliances provide an easy way to deploy applications and are well-suited to the task of backup. There are many products on the market already, and in terms of product selection the best approach is to look at the features offered by the backup application to determine if they meet requirements—a task that would be performed regardless of whether an appliance is being used.
For the right situations, virtual backup appliances are a good choice. But be careful of issues around performance and ongoing manageability as in the long run they may outweigh the benefits initially provided by going down the appliance route.
This was first published in July 2011