In part 1 of this article, I recounted the discussion between a reseller partner friend and me concerning differences between the physical and virtual backup appliances from Unitrends. I’m going to continue with the same conversation below. This picks up on the last set of questions which concerned feature differences between the Unitrends Enterprise Backup™ virtual appliance and the Unitrends Recovery-series physical backup appliance.

To recount just the feature section, while most features are the same between the the physical and virtual backup appliances there are differences. The most important difference is that with the physical appliance your support covers everything – including not only responsive support (when you e-mail or call us when there’s a problem) but proactive support (when we e-mail or call you when there’s about to be a problem) as well.

  1. Do you support hardware-based alerts on the virtual backup appliance as you do on the physical backup appliance?  No, we don’t. The hypervisor and the general nature of the hardware underlying the hypervisor prevents this.
  2. How about other differences beyond the responsive and proactive support for the hardware? You’ve already talked about licensing. Are there other differences?  Yes. One of the differences which I’ve discussed over at the blog in the post Unitrends Enterprise Backup and Cross-Vaulting (Bidirectional Replication) is that the virtual appliance doesn’t support cross-vaulting. The reasoning is architectural and is pretty simple – the reason our physical appliances support cross-vaulting is to split the physical backup appliance storage into two parts. This isn’t necessary on the virtual appliance – storage can be allocated to a local backup appliance and a vault (replication) target at will.
  3. Are there other architectural differences?  The physical backup appliance has what is called a “scale-out” architecture – it means that to get more backup and other features, you just add another physical backup appliance. The virtual appliance supports this – but also supports what’s called a “scale-up” architecture – which means you can add more underlying hardware (e.g., CPU, RAM, storage, network adapters, etc.) to handle larger backup and associated requirements.
  4. So what you mean is that you can’t add storage (or whatever) to the physical backup appliance?  That’s right in terms of the backup media pool to which you directly back up. You can of course add all sorts of archive space to either the physical or virtual backup appliance.
  5. You previously mentioned that the virtual backup appliance had no retention limits in either protected capacity or protected resource licensing models. Is deduplication the same between the physical and virtual backup appliances?  The deduplication approach and algorithms are the same; however, there is a fundamental difference. The virtual backup appliance allows different physical storage to be added via an advanced logical volume manager. Since our deduplication happens at the logical volume management level, this means we fit the SNIA description of global deduplication with our virtual backup appliance.
  6. How big a deal is this global deduplication in your virtual backup appliance?  It’s a big deal as the amount of data being protected grows – what it allows is larger amounts of data to be protected more efficiently.
  7. Any downside to global deduplication?  Sure. The problem with global deduplication is that if you’re not really careful in how you architect it that it can be a bottleneck in your system. In essence, the overhead of doing deduplication globally can offset the efficiency if you’re not careful.
  8. What do I do about that downside?  You use scale-out techniques with either the physical or the virtual backup appliance. That means a layered global/local deduplication scheme if using only Unitrends appliances. You can also move to a third-party deduplication-only device (like Exagrid) to simplify the architecture as your data grows.
  9. Any other differences in deduplication – or compression or encryption for that matter?  No.

We will continue with more of this conversation in the third and final part of this series next week, so stay tuned.