George Crump posted an article over on Network Computing discussing why storage is different for data protection. He makes a number of points regarding the benefits of using a storage appliance approach versus a software-only model, and for the most part, I agree with his analysis. However, there is an important point missing.
The software-only model relies on a generic software stack that can use any hardware or storage platform. This extreme flexibility also creates extreme headaches. The software provider or ISV cannot certify every hardware and environment combination and so the customer is responsible for installing, qualifying and testing their system. Initial setup can be difficult, but support can be even harder.
What happens if the product is not performing? The support complexities become difficult. Do you call your software ISV, your storage vendor, your SAN provider, your HBA vendor? There are a myriad of different hardware pieces at play and the challenge becomes how to diagnose and resolve any product issues. This is less of a problem in small environments with simple needs, and rapidly becomes an issue as data sizes grow.
The other challenge is managing change. The end user needs a solution that can adjust transparently to changing requirements such as stricter SLAs, new applications or data growth. The software-only model places the burden of system management and growth on the end user. Growing these solutions may not sound difficult, but typically involves purchasing and configuring multiple disparate pieces of hardware and software including servers, switches, storage and software licenses. These problems get geometrically worse as systems grow in size.
Storage backup appliances simplify the situation tremendously. The vendor provides a fully qualified and supported solution with a single point of contact. If a problem arises, the appliance provider will address the issue directly thus avoiding the finger pointing issues that are common with multi-vendor solutions. As environments change, the vendor will simplify the process and provide a supported upgrade path. However, remember that scalability varies widely and so the upgrade path will be more transparent with some solutions.
In summary, pure software-based deduplication solutions can provide strong business value in smaller homogeneous environments. However, as data sizes grow, they rapidly become complex and costly to manage.