ScaleOut SessionServer

Rapidly growing, mission-critical, ASP.NET server farms demand fast, scalable, and globally accessible storage for Web session-state. Traditional storage alternatives do not meet the need. ScaleOut SessionServer is the answer. Incorporating the same distributed caching technology as ScaleOut StateServer, ScaleOut SessionServer delivers:

• fast access time which outperforms all "out of process" storage alternatives,
• scalable throughput that handles heavy access loads on the largest server farms and keeps response times low, and
• farm-wide access to session-state that eliminates the need for server affinity ("sticky" sessions).

ScaleOut SessionServer is fully transparent to ASP.NET applications and requires only a one-line configuration change to make it operational. It is also significantly less expensive (at least 3X lower cost and 10X lower cost/update for three-server farms) than failover database clusters. Together with an ideal combination of high performance, high availability, and ease of use, ScaleOut SessionServer offers the best session-data storage solution for e-commerce and other mission-critical services.

Fast, Scalable In-Memory Storage

ScaleOut SessionServer runs as a distributed, software service on every Web server in your server farm to automatically store ASP.NET session-state in memory and make it globally accessible across the farm. Its sophisticated, distributed caching technology speeds up access to data and automatically scales its throughput as the server farm grows. ScaleOut SessionServer keeps session-state close to your application and off of your back-end database server.

Once installed, ScaleOut SessionServer operates in a fully transparent manner to Microsoft ASP.NET applications, saving and retrieving session-state objects for Internet clients. It automatically balances the amount of storage used by each server in the farm, adjusting the relative usage by each server to the amount you require. As new servers running ScaleOut SessionServer are added to the Web farm, they automatically expand its storage capacity and performance.

Breakthrough Performance

ScaleOut SessionServer combines fast, in-memory storage with distributed caching to deliver the fastest possible access time of all "out of process" solutions, including database servers and stand-alone caching servers. Performance tests have shown that ScaleOut SessionServer quickly outpaces its competitors in repeatedly accessing stored data.

What really sets ScaleOut SessionServer apart from its competitors is its ability to scale both its storage capacity and throughput as your server farm grows. As Web farms grow to handle additional load, they need to avoid bottlenecks that limit scalability. ScaleOut SessionServer is designed from the inside out to scale every aspect of its performance. Tests confirm that its throughput linearly scales to keep access times low as servers are added to the farm. This lets your Web farm deliver the highest possible performance while simultaneously keeping session-state access loads off of your database server.

Patent-Pending Technology for High Availability

High availability of session-data is essential for mission-critical Web farms. ScaleOut SessionServer ensures that sessions are never lost - even if a server in your farm fails - by replicating session-state on up to two additional servers. If a server goes offline or loses network connectivity, ScaleOut SessionServer automatically retrieves its session objects from replicas stored on other servers in the farm, and it creates new replicas as necessary to maintain redundant storage. To avoid the "split brain" problems of traditional master/slave replication schemes, ScaleOut SessionServer employs patent-pending technology which guarantees that replicated objects always have the latest updates.

ScaleOut SessionServer also uses a patent-pending, scalable heartbeat protocol that quickly and efficiently detects server failures without flooding your network with multicast heartbeat packets. Heartbeat failures automatically trigger ScaleOut SessionServer's "self-healing" technology, which quickly restores access to session-data and dynamically rebalances the storage load across the farm.

Seamless Integration

ScaleOut SessionServer works seamlessly with the Web farm's IP load-balancer. Since all servers can access any session-state object, it eliminates the need for the load-balancer to maintain "server affinity" with individual clients. This boosts performance by allowing client requests to be more evenly distributed across the farm. It also avoids the potential loss of service that could result if a client's workload data were stored only within a single server and the server fails. Also, the load-balancer can lose server affinity when client IP addresses change mid-session; ScaleOut SessionServer lets the application sidestep this problem.

Simplified Management

ScaleOut SessionServer self-managing features make installation quick and keep your management costs low. Servers automatically join together to form or expand a "farm-wide" store. Since all stored objects are accessible from any server, your load balancer can direct Web requests to any server in the farm. ScaleOut SessionServer automatically balances its workload to maintain high performance, and it automatically recovers and "self-heals" after a server fails.

You can manage ScaleOut SessionServer from any server in the farm or from a remotely connected workstation using its easy to use GUI console or a command line control program. These management tools give you complete control over ScaleOut SessionServer operations, notify you of failures and configuration changes, and ensure close coordination with your Web load balancer.

The Best Session-State Storage Option for ASP.NET

Microsoft's ASP.NET gives you several storage options for session objects. With its fast response time, scalable design, highly reliable storage, and cost-effectiveness, ScaleOut SessionServer offers the best solution for storing ASP.NET session objects. No changes are required to your ASP.NET programs since ScaleOut SessionServer transparently saves and restores session objects on each Web access. Performance tests have shown that ScaleOut SessionServer can improve overall Web response times for e-commerce applications by more than 6X over the use of a backend database server to store session objects:

The following table summarizes the advantages of using ScaleOut SessionServer instead of a database server (DBMS), a stand-alone, in-memory storage server, or ASP.NET's default, "in-process" method for storing session-state:

ScaleOut SessionServer is fully compatible with both ASP.NET 1.1 and 2.0.

The Next Step: Integrated, Distributed Caching

Developers who need to obtain the best possible application performance can upgrade to ScaleOut StateServer and access its comprehensive .NET and C/C++ APIs. For example, applications can use the APIs to boost performance by separately storing and update selected session data, such as large datasets, only as needed instead of on every Web hit as part of ASP.NET session-state. In addition, the APIs can be used to directly cache recently accessed database data and other fast-changing application state.