One the problems many organizations are increasingly facing is discontinuity that exists between on-premise and public cloud systems. System administrators often struggle and even sometimes fail to integrate their current local applications and data with their remote cloud services. Those that do find some level of integration often use workarounds and patches to accomplish it.
Several cloud service providers have acknowledged this problem and are working to provide their customers with integrated hybrid cloud solutions or even federated cloud solutions. Unfortunately, if you are on a tight budget and running a small business, for example, these options might be out of your price range.
Another option is to use a free and open source solution that is designed to create the same type of hybrid or federated cloud system. Many times, these software solutions may not come with the same support or guarantees that commercial vendors may offer, but some have impressive community support behind them and proven software that can make integrating your legacy systems with your new cloud ones less daunting.
To effectively integrate your on-premise and cloud systems, you need to make sure they can connect to each other without constant manual intervention. In other words, having to FTP your locally-changed data should be unnecessary. The other important aspect of integration you need is validation. Even if you successful sync data between one and the other, you need some way of verifying that data in one location is the same as the data in the other. Any software solution you choose should at least have those features.
Cloud computing is supposed to save you money, so if you can avoid having to spend thousands on an integration system, that is all the better. If, however, money is no object and you want a true hybrid or federated cloud and also need the support and SLA-type guarantees, a commercial offering may be your best bet.