In general, we've found that there are three primary obstacles to using WAN acceleration to serve branch offices.
The first is that WAN acceleration just isn't a good solution for write-intensive applications. At first glance, bank branches would seem to be a WAN acceleration win. However, since tellers scan images of every deposit, there is a large amount of unique write data that overwhelms the small amount of cache in a typical WAN acceleration appliance.
The second obstacle is that most organizations have some applications that don't use protocols that WAN acceleration devices can sufficiently optimize. If all you need to do is provide a low-performance file server and allow users to access the Exchange server via Outlook, a Riverbed Steelhead, the company's core WAN acceleration technology, might be a great solution. However, if you have to run some legacy application that the Steelhead appliance can't compress, deduplicate and accelerate, the users are going to have an unhappy experience.
Then there is the third and perhaps biggest obstacle: Most WAN acceleration solutions don't provide access to your data if the WAN link is down. Personally, I never trusted my telco providers enough to be willing to live with the no-win, no-work scenario.
Granite is an iSCSI storage device that acts as a cache to storage in your data center. With Granite you can run a domain controller, file server and the like in the branch office. Granite will provide storage for the servers, and it will synchronize the data to iSCSI storage in your data center through a Granite core appliance. Since this is a Riverbed product, the data will be compressed and deduplicated using Steelhead.
In some ways, Granite is the enterprise version of an iSCSI-based cloud storage gateway like those from StorSimple or TwinStrata drop. While those appliances provide a cache-to-front-end-to-object-based cloud storage, Granite uses block storage in your data center for its ultimate repository. Unlike the cloud gateways' logical volumes, or LUNs, Granite appliances' aren't limited to access by a single server. The folks at Riverbed tell me that Granite supports SCSI bus resets so servers at the branch office and servers in the data center can be part of a single cluster, or LUNs can be pinned to the Granite to enable off-line access.
Granite would be cool if it was a dedicated storage appliance, but the best part is that Riverbed has implemented it as an application on its new Steelhead EX appliance line. Not only does this mean that a single appliance can handle storage and other WAN acceleration tasks, but since the Steelhead EX runs VMware, that appliance can also host the servers you need in the branch. Riverbed has Steelhead EX appliances with up to 4 Tbytes of storage and 64 Gbytes of RAM, which should allow most branch offices to run their entire operation from a single appliance.
Riverbed's Edge Virtual Server Infrastructure (E-VSI) is just one of the innovative solutions I've seen recently for simplifying the process of managing data in remote offices. With cloud and other virtualization technologies advancing at a rapid clip, there's no excuse for five physical servers and a tape drive for backup in your branch offices anymore.
Disclaimer: Riverbed is not a client of DeepStorage, but Riverbed reps have bought me lunch occasionally.