White paper Cutting datacenter costs with server and infrastructure offload A technical guide
Table of contents Overview Primary mechanisms for server offload... 4 Secondary mechanisms for reducing and better managing server load... 5 Cutting the cost and complexity of other datacenter infrastructure... 6 The NetScaler difference... 6 Summary
Overview Enterprises and service providers worldwide are struggling to deal with mounting datacenter costs. For those paying the bills, the prevailing trends resemble a perfect storm. Server count continues to grow at the relatively high rate of ten percent per year as organizations seek to further automate business processes and increasingly embrace compute-intensive, multi-tier Web application architectures to do so 1 ; Once distributed computing resources are now being centralized within datacenters to ease compliance efforts, improve security, and help address heightened requirements for disaster recovery and business continuity; and Power and cooling requirements for servers and other hardware continue to rise in response to demand for systems with higher performance. Citrix NetScaler Available as a family of highly scalable, purpose-built appliances, Citrix NetScaler is a full-featured Application Delivery Controller. By combining a highly complementary set of functional modules, NetScaler enables organizations to optimize and ensure the performance, availability and security of both their public-facing and intranet Web applications. A marketproven solution, NetScaler is used by 8 out of the 10 largest Web sites and over 2,000 enterprises. An estimated 75% of Internet users hit a NetScaler daily. The net result is that datacenter power demand is doubling approximately every five to six years 2 at the same time that energy prices are increasing five percent per year, and possibly even more going forward. Moreover, many organizations are facing the prospect of paying for entirely new datacenters as their existing ones simply run out of available floor space or power and cooling capacity. For those already at their limits, this approach also means having to get by as best they can for the next two to three years, or however long it takes for their new data centers to be designed, approved, constructed and eventually brought on line. Without the capacity to readily deploy new applications, a key ingredient for remaining competitive, the impact to these businesses could be devastating. One remedy is for IT to find ways to reduce the number of required servers without compromising the services and applications that are delivered to the organization. In this regard, taking advantage of server virtualization technology is clearly a popular option. However, the use of an Application Delivery Controller, such as Citrix NetScaler, is an equally promising approach that also deserves close consideration. With a powerful set of capabilities for offloading datacenter infrastructure, NetScaler 1 Source: US EPA Energy Star Report to Congress, 2007 2 Source: US EPA Energy Star Report to Congress, 2007 3
provides a relatively quick, low-cost way for organizations to cut their server count by 50 to 60 percent or more. Significant cost savings are in turn accrued from a corresponding reduction in datacenter requirements for space, cooling, power and personnel. Primary mechanisms for server offload Deployed in front of application servers, NetScaler delivers a number of significant benefits. Chief among these is the ability to help control datacenter costs by substantially reducing the number of servers that organizations require to deliver their applications. From a technical perspective, this is accomplished primarily by the following set of features, each of which frees back-end systems from one or more resource-intensive operations. TCP multiplexing Ordinarily, application servers have to set up, maintain and tear down multiple TCP connections to fulfill a single, user-level transaction. This is especially true for Web applications, where individual pages often comprise numerous objects and a single click can entail tens or even hundreds of back-end requests. The resulting drain of all these TCP operations in terms of both CPU cycles and memory usage can be considerable. TCP multiplexing is a connection management capability that can relieve application servers of a significant portion of this burden. In its role as a proxy between clients and servers, NetScaler is able to track HTTP requests independent of TCP connections. This affords the opportunity to aggregate a large number of requests, even ones from different clients, over a much smaller number of long-lived TCP connections, even if the clients do not support persistent connections. As a result, each server s connection handling responsibilities are dramatically reduced. Buffering, a closely related TCP management capability, eliminates the server s dependency on the client s connection speed. With buffering, once a request had been made to a server, the response can be sent to NetScaler at full LAN speeds. NetScaler then throttles the response at whatever rate the client requires, effectively freeing individual servers from another onerous connection management task. It offloads the TCP handling from the servers onto the NetScaler appliance, meaning less server infrastructure is needed to support a huge load. Mike Jones, CEO, Userplane For Userplane, this translated to needing only 20 of an estimated 150 servers to host a new Web-based system, thereby avoiding an outlay of $390,000. SSL offload Heightened concerns for the integrity and confidentiality of sensitive data means that an increasingly significant percentage of application content must be encrypted. Associated key exchange, certificate management and bulk cryptographic operations are all relatively compute-intensive processes. However, with its hardware-based SSL acceleration capabilities, NetScaler is able to offload these functions, freeing server resources for other tasks. Performing these cryptographic operations is also essential when it comes to maximizing the benefit of the other offload features discussed herein. Many of these features depend upon having access to packet payloads, not just headers. So without the SSL offload capability, they would only be able to operate on unencrypted application traffic. Caching Particularly with Web applications, many of the requests being received are for the same bits and pieces of content. As a result, caching is another highly effective means for reducing the load on downstream servers. In the case of NetScaler, the gains are maximized due to the fact that its AppCache TM functionality provides in-memory caching not just for static data, but for dynamically generated HTTP application content as well. In addition, highly flexible rules can be configured to granularly define content cacheability and set expiration (i.e., forced refresh) timeframes. 4
Depending on the nature of the application being served, each of these mechanisms TCP multiplexing, SSL offload and caching is capable of substantially reducing the load placed on the corresponding servers. When they are used in combination, organizations will often see their server requirements cut by a factor of two to three, or possibly even more. For example, implementing NetScaler allowed Live Nation, a U.S.-based promoter and producer of live events, to manage its site traffic with 50 percent fewer servers. In another case, SINA, a leading online media and value-added information services provider serving Chinese audiences worldwide, deployed NetScaler and was able to reduce the number of servers required to support its Web site by 66 percent. I don t have to have as much hardware behind the site. It s a huge benefit that NetScaler can manage front-end connections and maintain persistent connections to the back-end. Without NetScaler, we would probably need at least twice as many servers. This saved us close to six figures in hardware and other costs. Jim Hayes, VP Data Center Operations, Live Nation Secondary mechanisms for reducing and better managing server load This next set of server offload mechanisms is classified as secondary because the gains they yield are more likely to be incremental, particularly relative to the previously discussed primary mechanisms. This is due to these features having less applicability, as well as somewhat lower impact to begin with. Nonetheless, in a situation where every square foot, BTU, watt and dollar counts, they still deserve attention. Session persistence As part of its layer-4 load balancing functionality, NetScaler includes support for session persistence. This means that source IP address, cookies or various hashes can be used to ensure that all subsequent requests associated with a user s session can be directed to the server selected to process the initial request. By providing this capability, NetScaler relieves the application and its corresponding servers of the need to continuously share state information. Although state sharing is typically a non-issue for smaller implementations, it can actually be quite taxing for large applications that are spread over tens or even hundreds of servers. Server specialization Less about offloading and more about right-loading, server specialization is a by-product of NetScaler s layer-7 load balancing capabilities. Unlike conventional layer-3/4 load balancers, NetScaler can also route traffic based on application-layer attributes, such as HTTP header, uniform resource identifier, SSL session ID and HTML form data. For organizations that are interested, this difference can be used to enable more efficient utilization of its servers. In particular, because all of the services and components that comprise an application no longer need to be implemented on every server node, each physical system can now be tailored to the specific functions it will be supporting. Cost-based load distribution Similar to the previous mechanism, cost-based load distribution is also more about right-loading than offloading. However, no servers will be recovered in this case, only costs. NetScaler uses global server load balancing capability to selectively shift application loads that are already being supported by multiple datacenters to whichever datacenter has the most favorable cost conditions at any given point in time. For example, if one datacenter has lower power rates and can take advantage of free-cooling techniques during its evening hours, then it may make sense to shunt application loads its way instead of to a datacenter that is simultaneously operating during its daylight hours under far more adverse power, cooling and cost conditions. Obviously, this could be a tricky proposition. A full cost analysis would be appropriate and the potential impact on user experience would also need to be weighed. But for those scenarios where the conditions are right, the resulting cost savings can certainly be worth the effort. 5
Cutting the cost and complexity of other datacenter infrastructure So what about the rest of the computing infrastructure? After all, datacenters are not made up of servers alone. Not surprisingly, NetScaler can help there as well, in several distinct ways. First, there is the derivative impact of server offload. Having fewer servers will often enable an organization to get by with smaller or fewer network and security devices, such as switches and intrusion prevention systems, since fewer physical ports will be needed. Next, there is the impact of the following features, each of which improves end-to-end latency and lowers bandwidth and system capacity requirements. TCP optimization Whereas TCP multiplexing involves connections between NetScaler and back-end servers, other TCP optimizations are applicable at the front end. Techniques such as forward-error correction, window scaling and buffering help make more efficient use of bandwidth and reduce the amount of chattiness an inefficient application behavior that takes numerous back-and-forth exchanges between client and server to complete a single, user-level action. These mechanisms may not seem like much on the surface, but it is not uncommon to have them trim bandwidth by a third while also reducing latency by a factor of 2 to 10 times. Application-specific optimization Analogous to the previous feature, application-specific optimization is different only in that it involves overcoming efficiencies at higher layers of the computing stack, for example, with HTTP and the Web services family of protocols. Compression A common technique for shrinking the amount of data exchanged between clients and servers, compression reduces bandwidth consumption while simultaneously improving user performance. However, executing the corresponding algorithms in real-time is a processor-intensive task that can overload busy application servers. By integrating AppCompress, a high-performance compression engine, NetScaler relieves servers of this burden while also reducing the load for every network link and infrastructure device between itself and all of the application s clients. Finally, a third item to consider is that NetScaler itself provides a substantial degree of consolidation and, therefore, infrastructure offload. With modules for all of the capabilities described above, as well as ones for Web Application Firewall and SSL VPN technology, NetScaler enables a broad range of services to be implemented via a single platform. The alternative, having IT implement a collection of standalone devices, is considerably less attractive. It introduces far greater complexity, requires that many more power supplies to be fed, consumes more cooling capacity and incurs the performance penalty of having to process the same set of packets that many more times. The ability of Citrix NetScaler s AppCache to cache common server requests, combined with page compression and connection optimisation, has resulted in improved data transmission to end users. Citrix NetScaler has greatly reduced TfL s bandwidth requirements without the need to increase server hardware, power or data centre space. David Coppins, Group Marketing Operations, Technical Manager, Transport for London The NetScaler difference NetScaler is not the only Application Delivery Controller available in the market. When it comes to server and infrastructure offload and reducing datacenter costs, there are many other products that will claim to provide a similar set of capabilities. What sets NetScaler apart, however, is the efficiency with which it executes the aforementioned mechanisms and its superior scalability. What makes these differences possible are its unified management, purpose-built platform and integrated-yet-modular design. 6
Unified management Today s Web applications are extremely complex. This application complexity frequently leads to ADC configuration complexity. Beyond configuring basic L4 load balancing, it can be hard for a network administrator to even know where to begin when configuring an ADC for Web applications. The net effect of this is that for many applications, the offload and other optimization benefits of a solution like NetScaler frequently go untapped. AppExpert Templates new in NetScaler 9 mask this complexity by encapsulating all the elements of the NetScaler configuration specific to a given application. An AppExpert Template includes: 1) The application components (e.g., pages, files, archives, Web Services) that NetScaler will optimize 2) The traffic management entities (e.g., VServers/VIPs and associated load-balancing algorithms, health checks, persistence methods, SSL offload settings) for these application components 3) The specific NetScaler policies for caching, compression, rewrite and other NetScaler functionality used to optimize the application By using NetScaler AppExpert Templates, organizations can easily tap the full potential of NetScaler to cut server costs and optimize the application, regardless of its complexity. AppExpert Template main view and Application Configuration Visualizer. AppExpert Templates present a consolidated view of everything NetScaler is doing for a given application to NetScaler administrators, further simplifying management. From one place, NetScaler administrators can manage, maintain and change the NetScaler configuration for the application. This same view provides a framework for NetScaler administrators and their peers in the application groups to work together as existing applications evolve and as new applications are brought online. Perhaps most importantly, AppExpert Templates are designed to be imported and exported, so the benefits of NetScaler for specific applications can be gained within minutes. Import/export also makes it easy to share application-specific configuration within an organization and between organizations. 3 3 Pre-built AppExpert Templates are available for download from http://community.citrix.com/cdn/ns 7
NetScaler capabilities Server and infrastructure offload is just one of several strengths of the NetScaler application delivery solution. With its comprehensive set of functional modules, NetScaler also provides extensive services and helps IT address key requirements in the areas of application security, availability and performance. Available modules include the following: AppCompress EdgeSight AppCache SSL acceleration Content switching Global server load balancing Content rewrite Application security Access Gateway Citrix SmartAccess Load balancing AppExpert Templates are fully integrated with the intuitive NetScaler GUI and performance dashboard, and work seamlessly with the AppExpert Visual Policy Builder. The AppExpert Visual Policy Builder supports all NetScaler functionality via a common policy creation environment. Using the AppExpert Visual Policy Builder, any individual NetScaler policy can be created with no need for programming or scripting. Combined, NetScaler s unified management makes fully exploiting NetScaler offload easy. Purpose-built platform Offloading servers and other datacenter infrastructure means that NetScaler itself must tackle a variety of compute-intensive processes. To perform these better, more efficiently and in a more scalable manner, it must do things differently. It must apply a level of specialization that elevates its capabilities beyond those of ordinary application servers. For NetScaler, the key is having a purposebuilt platform, one where the hardware and, even more importantly, the system-level software have been constructed and optimized explicitly to support the previously discussed mechanisms and features. Some of the more significant elements this entails include: A customized hardware design, where both general-purpose processors and special-purpose merchant silicon are combined in a way that capitalizes on their individual strengths A customized operating system, where the conventional interrupt-driven model is replaced with a completely deterministic approach to connection management and packet processing, one that helps minimize latency and maximize scalability A customized TCP/IP stack, where extraneous routines have been eliminated and others have been finely tuned to deliver optimum performance An intelligent HTTP parsing engine, where packet-processing tasks need not be repeated for each individual service being supported (e.g., caching, compression) Integrated modular design Being modular is fundamental to the flexibility and functional scope of the solution, and to the overall value and economic benefit it has for IT (see sidebar). This is not enough, however. With NetScaler, emphasis is placed on ensuring compatibility and providing deep integration between the different functional modules. This way, each one is assured the opportunity to take full advantage of the embedded performance and security features of the purpose-built platform; and efficiency and scalability of the system can be increased even further. (For further details, readers are encouraged to review the whitepaper Advanced load balancing: 8 must-have features for today s network demands, available at www.citrix.com.) 8
Summary Most organizations are struggling with the high cost of datacenter operations. For many organizations, the situation is even worse. They have run out of space, power and cooling capacity, or soon will. Fortunately, Citrix NetScaler provides a way to address both issues in a quick yet sustainable manner. By taking advantage of NetScaler s extensive set of server and infrastructure offload capabilities, IT departments can realize a reduction of 50 to 60 percent in their server requirements, along with a corresponding cut in datacenter costs. Furthermore, because NetScaler is based on a purpose-built platform, features an integrated yet modular design, and is accompanied by robust management tools, organizations can be assured these gains will be maximized, particularly relative to competing solutions. Citrix Worldwide Worldwide headquarters Citrix Systems, Inc. 851 West Cypress Creek Road Fort Lauderdale, FL 33309 USA T +1 800 393 1888 T +1 954 267 3000 Regional headquarters Americas Citrix Silicon Valley 4988 Great America Parkway Santa Clara, CA 95054 USA T +1 408 790 8000 Europe Citrix Systems International GmbH Rheinweg 9 8200 Schaffhausen Switzerland T +41 52 635 7700 Asia Pacific Citrix Systems Hong Kong Ltd. Suite 3201, 32nd Floor One International Finance Centre 1 Harbour View Street Central Hong Kong T +852 2100 5000 Citrix Online division 6500 Hollister Avenue Goleta, CA 93117 USA T +1 805 690 6400 www.citrix.com About Citrix Citrix Systems, Inc. (Nasdaq:CTXS) is the global leader and the most trusted name in application delivery infrastructure. More than 215,000 organizations worldwide rely on Citrix to deliver any application to users anywhere with the best performance, highest security and lowest cost. Citrix customers include 100% of the Fortune 100 companies and 99% of the Fortune Global 500, as well as hundreds of thousands of small businesses and prosumers. Citrix has approximately 6,200 channel and alliance partners in more than 100 countries. Annual revenue in 2007 was $1.4 billion. 2008 Citrix Systems, Inc. All rights reserved. Citrix, NetScaler, Access Gateway and EdgeSight are trademarks of Citrix Systems, Inc. and/or one or more of its subsidiaries, and may be registered in the U.S. Patent and Trademark Office and in other countries. All other trademarks and registered trademarks are property of their respective owners.. 1008/PDF www.citrix.com