Virtual backup appliance pros and cons

Computer Weekly examines virtual backup appliances that run backup and restore from a virtual machine

Most organisations these days prefer to deploy most new servers as virtual machines (VMs), with physical servers deployed only in exceptional or business-justified cases.

Virtual backup appliances – part of a family of virtual storage appliances (VSAs) – are one example of VMs that can deliver the features of traditional hardware appliances.

The term “appliance” is used where the installation of these products is packaged, as an abstraction above the underlying operating system that doesn’t require the customer to build and manage a VM before deployment.

Virtual backup appliance pros and cons

What’s the point of using a virtual machine installation of a backup product in place of the real thing? There are some clear advantages, such as cost, flexibility, compatibility, performance and the opportunity to try before you buy:

+ Cost

A software version of a backup appliance doesn’t require any hardware to be shipped, making the product cheaper to acquire. In addition, there’s no cost associated with power, cooling or datacentre space, although some IT departments may charge for the deployment of a VM.

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+ Flexibility

Deploying a virtual machine in certain environments (such as a remote office) can be easier than installing and supporting a physical appliance. In addition, virtual appliances can integrate with management tools such as VMware’s vCenter to provide a streamlined system. There is also a time-to-deployment benefit from implementing a virtual appliance, because they are usually quicker to implement and configure than traditional backup products.

+ Compatibility

Using the virtual version of a physical appliance provides compatibility between both product form factors. This means, for example, that native replication of backup data from remote virtual appliance installations into a central physical configuration is possible. In addition, virtual appliances can usually be monitored and managed from the same console as their physical counterparts.

+ Performance

Integrating the backup appliance into the virtual infrastructure means data doesn’t have to traverse the physical network. When configured and architected correctly, this means virtual appliance backups can be faster than those using a physical device.

+ Try before you buy

Most suppliers offer trial versions of their virtual backup appliances. The ability to run a virtual backup appliance for 30 or 60 days allows customers to see, without incurring costs and at little risk, whether such a product would work in their environment.

There are, however, some disadvantages to the virtual appliance model, such as performance, maintenance, compliance and virtual machine sprawl:


The CPU and memory demands of a virtual backup appliance may limit the performance that could be achieved compared with a physical machine. The virtual appliance could also be a drain on hypervisor resources on which it is deployed.

Maintenance and compliance

Deployment as an appliance means the VM’s application code is not accessible to the customer. This can prove a problem when carrying out functions such as network hardening, upgrades and maintenance, as well as meeting datacentre compliance standards for configuration.

VM sprawl

The ease of deploying virtual appliances can create problems with VM sprawl, where many virtual machines proliferate across numerous hypervisors. This leads to issues in tracking which virtual backup appliances are backing up or storing data from which virtual machines and so requires some manual tracking. Administrators need to spend time planning the use of virtual appliances to ensure backups and data are tracked effectively.

Virtual backup appliance supplier roundup

There are two main product types of virtual backup appliances. First, there are backup target devices, used to store and optimise backup data using features such as data deduplication and compression.

The second form deploys pre-configured backup software in a virtual machine, but typically needs additional storage (provided from the hypervisor or externally) to retain backup data.

These systems are analogous to deploying a virtual machine then the backup software, but save the customer time and effort in deployment and configuration.

Providers of virtual backup appliances include:


EMC provides a virtual backup appliance of its Avamar data deduplication appliance. The virtual edition provides capacity for up to 4TB of disk space and supports all existing Avamar features, making it suitable for remote office deployments that already use VMware ESXi infrastructure. The Avamar platform supports features such as global data deduplication and optimised wide area network (WAN) links, allowing the virtual appliance to replicate data into a central core infrastructure.


Falconstor has a number of backup products, including its CDP (Continuous Data Protector) Virtual Appliance. This product is supplied in open virtualisation format (OVF) – and so deploys on VMware vSphere environments – with a usable backup storage capacity from 1TB to 10TB in 1TB licence increments. CDP provides direct iSCSI access, but can be configured to work with Fibre Channel networks, depending on how the host hypervisor is configured. Features include application-aware snapshots (via guest agents), up to 255 snapshots per disk image, data journaling, thin provisioning, data mirroring (both synchronous and asynchronous) and WAN-optimised replication with encryption.


Zmanda, acquired by Carbonite in 2012, provides a backup appliance that comes pre-configured with a copy of Amanda Enterprise Edition backup software. Supplied as an OVF, the appliance is supported on VMware vSphere environments. Storage is configured to the appliance through any host method – network-attached storage (NAS), direct-attached storage (DAS), iSCSI, for example – and tape drives are also supported. The appliance is a full-featured copy of the Amanda Enterprise Edition software, which includes support for common applications such as Exchange Server, SQL Server and Oracle. The appliance also supports writing data to Amazon S3 as a storage target. Pricing is based on the support model with three options – basic, standard and premium – available.


Quantum offers two virtual appliance versions of its DXi backup appliance. The DXi V1000 supports up to 30TB effective capacity, based on an assumed 15:1 data deduplication ratio and a maximum 2TB usable storage. The DXi V4000 supports up to 24TB usable and 360TB effective capacity. The DXi v4000 has a higher data ingest performance than the DXi V1000, but that is achieved with a higher specification of virtual machine – 48GB versus 4GB of vRAM and eight virtual cores compared with two cores, respectively. As a result, the DXi V1000 is targeted at remote offices whereas the V4000 can be used for datacentre deployments. Both systems support data deduplication, replication and data encryption.


HP offers a virtual storage appliance option for its StoreOnce platform. Two options are available that support capacities up to either 4TB or 10TB. These options require 16GB or 32GB of vRAM respectively, with both systems requiring four vCPUs and dual GbE vNICs. The StoreOnce VSAs are supported on both VMware vSphere and Microsoft Windows Server Hyper-V R2. StoreOnce VSA provides all the features of the physical appliance equivalent, including deduplication and the connectivity through network file system (NFS), common internet file system (CIFS), virtual tape libraries (VTL) and StoreOnce Catalyst. HP does not support StoreOnce VSA with Fibre Channel connections.


STORServer offers two virtual appliances that deploy with backup software from CommVault and IBM Tivoli Storage Manager respectively. Both systems deploy a virtual machine with the backup software pre-installed and so support all the standard features of both platforms.

Arkeia Software 

Arkeia Software, now part of Western Digital (WD), provides a number of virtual appliances for backup. The WD Arkeia Virtual Appliance supports VMware vSphere environments and provides standard backup capabilities with support for more than 200 physical server platforms. The system includes data deduplication that operates globally across multiple hypervisor environments. As a target for data, the WD Arkeia appliance supports backup to local disk and tape media, as well as to public cloud storage as part of an offsite system. Arkeia also provides virtual appliance support for its VMware vStorage Backup Agent. This provides additional backup functionality for vSphere virtual environments, including block-level and file-level restore granularity.


Axcient, a provider of backup as a service and recovery as a service now offers a virtual appliance of its existing hardware products. The virtual appliance connects to Axcient Cloud and allows customers to write backups directly offsite into Axcient’s public cloud infrastructure. Axcient’s backup appliances provide support for the major virtual server environments, such as vSphere, Hyper-V and XenServer, as well as common applications, such as Microsoft SQL Server, Exchange and SharePoint. Pricing is based on level of support and backup features, with a free version providing local backups only.

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