ScaleOut GeoServer

With version 3.0, ScaleOut StateServer extends distributed caching across multiple, geographically distributed data centers using ScaleOut GeoServer™. This option, which is licensed separately from ScaleOut StateServer, replicates stored objects between ScaleOut StateServer stores running on server farms at different sites. This enables multiple data centers to share fast-changing workloads and stay fully protected against site-wide failures. GeoServer's capabilities help IT managers meet the stringent performance and uptime needs of high-end Web sites and other mission-critical applications.

The Need for Multi-Site Replication

Web-based services and other key applications often run on server farms in one or more data centers and employ distributed caching to optimize performance. An increasing number of companies employ multiple data centers to improve their quality of service and to help mitigate the impact of catastrophic events such as earthquakes and floods. If one data center goes offline, its workload can be handled by another, healthy data center to avoid service interruptions.

For this recovery strategy to be effective, changes to cached application data must be continuously replicated to a remote site so that it is immediately ready to handle the workload. ScaleOut GeoServer enables server farm applications that use ScaleOut StateServer's distributed caching to quickly and efficiently replicate cached data to a remote server farm for immediate access after a site-wide failure. In addition, two sites can share a common, fast-changing workload using bi-directional replication.

Straightforward, Flexible Usage

ScaleOut GeoServer configures easily to keep management overhead low. To start replication, the user simply connects to a server on a remote farm using an existing virtual private network or other secure communications channel. ScaleOut GeoServer automatically configures itself to distribute traffic among servers within the remote server farm and then forwards storage updates to the remote farm. As servers are added or removed at each farm, GeoServer automatically reconfigures its network connections to maintain the best possible replication performance without the need for manual intervention.

For maximum flexibility, objects created using ScaleOut StateServer's APIs optionally can be tagged to disallow replication. (ASP.NET session objects are always replicated to remote stores.) All object attributes, including timeouts, LRU behavior, and dependency relationships are replicated to the remote site.

Fast, Scalable Architecture

Unlike most replication solutions, GeoServer uses scalable and highly available connections that take full advantage of all servers in each farm. To maximize performance and availability, all servers within both the local and remote StateServer farms participate in data replication.

When replication to a remote store is started, all hosts within the local ScaleOut StateServer (SOSS) store are notified to begin replication. Each local host first establishes a TCP connection to one of the servers in the remote store; an initial connection can be established even if one or more remote hosts are offline. All local SOSS hosts then automatically download a list of the hosts that form the remote store. In addition, they download load-balancing information that is used to most efficiently direct object updates to individual hosts in the remote store. This information is automatically updated whenever a membership or load-balancing change occurs at the remote store. Now the local SOSS hosts can begin forwarding object updates to the remote store.

Since all local hosts participate in handling local object updates, they simultaneously replicate these updates to the remote store. This maximizes both the throughput and scalability of data replication. Likewise, it ensures that data replication not interrupted if hosts in either local or remote store should fail. GeoServer replication automatically scales its replication bandwidth to deliver the best possible performance and availability.