The Big Role of Physical Backup Appliances


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By Jim Whelan and Christine Taylor, The Taneja Group

Virtual backup appliances (VBAs) are an instance of backup software running in a virtual machine on a general purpose server. VBAs are flexible and effective, and they are usually simple to deploy. Having said that, physical backup appliances (PBAs) have distinct advantages in several areas.

PBAs consist of a self-contained, tuned hardware platform which has everything you need to perform backups and recovery already installed on it, including compute, storage and software, making it a plug-and play-solution. Capacities generally range from under 10 TB to larger appliances offering more than 200 TB, making them attractive to customers ranging from SMBs all of the way up to the enterprise.

Why Consider a Physical Backup Appliance?

In today’s increasingly more virtualized world, many people ask why they should consider buying a physical appliance when they can just set up a virtual backup appliance running on one of their existing servers. There are a number of considerations to take into account where PBAs can give you an advantage:

  • Resource Usage.Since a VBA is simply a specialized virtual machine running on a host server, it’s sharing the hardware resources of the server with other VMs running production workloads. There is no such thing as a free lunch; if IT runs a VBA on the same server that production VMs are running on, everything runs slower because of resource sharing and contention. When backups initiate, they can cause a noticeable slowdown in performance of the production VMs. A PBA with dedicated hardware will not share resources with VMs, and it will run backups and recoveries without impacting the virtualized resources.
  • Hardware Isolation.PBAs provide hardware isolation that VBAs can’t. If IT is running a virtual appliance and experiences a fault in the virtualization system, it affects all of the VMs, including the VBAs. By definition, a PBA is separate from the virtualization environment. This makes PBAs far more effective in protecting backups from virtualization faults than a VBA.
  • Performance.As flash memory prices have dropped, some PBA vendors are adding flash to their physical appliances. By choosing an appliance that combines flash with spinning disk, users can expect to see noticeably better backup performance than they’ll see with VBAs or disk-only PBAs. Also, because of their dedicated hardware, physical appliances can often run more backup threads in parallel than a corresponding virtual appliance.
  • Simplicity.The PBA should be simple to set up with the factory or reseller doing the integration beforehand. Make sure that the vendor has engineered it to be truly plug-and-play so that it can be installed and booted up in a short period of time. The management console should be easy to operate and should manage both PBAs and VBAs from the same vendor to maintain flexibility in running a mix of physical and virtual appliances. Equally essential, the PBA should have deduplication, encryption and compression capabilities built in. Some vendors offer these capabilities separately, adding unnecessary complexity cost.

The Role of Flash in PBAs

Today, the use of flash memory in many different primary storage products is quite common. However, Unitrends Recovery-Series backup and recovery appliances are unique in using tiered flash in their storage architecture to increase their performance.

Their implementation consists of a solid state disk (SSD) used as a second-layer cache device for the rotational storage. The SSD is used to smooth out uneven I/O streams to optimize the performance of the rotating disks. It’s also pressed into service for handling the metadata used in backup, recovery and deduplication processing. These activities are all heavily read intensive, so keeping the metadata in the SSD yields substantial performance improvements. Unitrends testing shows roughly 300 percent faster backup times and 125 percent faster restores with the flash tier in place.

Their cache management algorithms also ensure that the user is never exposed to a flash failure. The SSD can literally be pulled out of the box with no data loss, only a drop in performance, so users are able to benefit from the improvements without worrying about reliability.

Not all of the Recovery Series appliances contain flash; the smaller, desktop boxes don’t need it given their target customers. It’s included in all of the bigger rackmount boxes, however, so that customers needing to support a high level of concurrent backup, recovery and deduplication activity on a single box will be able to do so with class-leading performance.

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