Monday, April 6, 2009

Data Domain - Appliance or Gateway?

Customers looking to purchase a Data Domain solution often ask whether or not they should buy an appliance or a gateway. We recently spoke about this with the technical folks at Data Domain and here is what we found.

From a feature functionality standpoint the appliance and gateway models are the same. There is no difference in terms of scale or performance. Both the 690 gateway and the 690 appliance deliver up to 2.7 TB /hr of throughput and offers data protection capacities up to 1.7 PB. The lack of difference in performance is a bit surprising since the appliance uses software based RAID, which of course is offloaded to the external array in a gateway solution. One would expect that the gateway approach would perform better since the internal processors would be free to handle other tasks such as IO operations. However this doesn’t appear to be the case.

The biggest difference then is in terms of the overall experience with the solution. In an appliance based solution Data Domain is responsible for all of the code and software updates. The appliance interacts directly with the disk and Data Domain has tweaked the drivers for optimum performance and included mechanisms to ensure reliability. In the gateway approach, the Data Domain interaction stops at the HBA. The result is that the overall user experience is now dependent on not just Data Domain but the external array. In order to ensure that the experience is positive Data Domain provides best practices for using external arrays, including a list of supported arrays, microcode levels and recommended configurations.

Once deployed it simply means that the administrative group will have more items to consider. Compatibility will need to be verified before microcode upgrades on either the array or the Data Domain. If the external array is to be shared with other hosts care must be taken to ensure that these hosts do not impact the Data Domain environment.

At the end of the day, if you already own a supported array that meets the requirements then using a gateway will likely save you some money, otherwise it probably makes sense to stick with an appliance.


  1. the big kicker is....which is cheaper, dd sata or sata from hds/sun/emc/(insert vendor)?

  2. A valid question; and I have not done any actual comparisons. But considering probalby the largest two costs associated with storage arrays (from any vendor) is the initial cost of the head or controller unit, and the maintenance; I would expect to see the appliance version win out in overall TCO. Perhaps a different story for a company that own's some older arrays that are no longer in 'production', or a company that does self-maintenance and doesn't have monthly or yearly support costs on the storage.