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OverviewData replication has become a common process within most enterprise IT departments. The need to protect critical data and ensure continuity of operations drives companies to deploy sophisticated replication solutions that meet very specific SLA objectives, such as EMC Symmetrix Remote Data Facility® (SRDF). However, meeting these SLA objectives is not always easy. In addition, more and more replication deployments are relying on IP Wide Area Networks (WAN). The performance of these WANs has a direct impact on data replication SLA performance, also known as recovery point objectives (RPOs) and recovery time objectives (RTOs). F5 Networks provides a market-leading WAN optimization solution that significantly improves data replication (DR) performance between remote data centers without the need to add additional WAN bandwidth. Specifically, the F5 WANJet 500 appliance has proven effective in helping customers improve the performance of EMC SRDF, and has been extensively tested and approved by EMC’s E-Lab for compatibility and performance with SRDF/Asynchronous and SRDF/Data Mobility modes. WANJet is also available for purchase through EMC Select for a total replication solution from EMC.

Challenges Affecting Data Replication Performance and ReliabilityData replication across geographically dispersed data centers with minimal risk of downtime is a growing requirement for many businesses. Distances between data centers continue to expand due to data center geographical placement considerations, increased regulations, and risk management. There is an increased business sensitivity to data loss, and risks that might have been acceptable ten years ago are no longer acceptable. In addition, the volume of data being replicated is growing dramatically, leading to increased data replication traffic being transmitted over the WAN. Add to all of this the ever-present budget limitations, and it can make data replication solutions quite complicated.

The performance of most data replication solutions depends heavily on the performance of the WAN. WANs, however, can be notoriously fickle with varying latency, packet loss, and congestion levels over time. As a result, most companies feel the need to over-purchase their WANs, which can help with performance, but can result in much higher expenses than necessary. According to a recent Forrester Research report1, WAN bandwidth can represent as much as one-third of the total replication project’s ongoing costs. It’s hard for business to anticipate the need for increased bandwidth, and replication solutions can require bandwidth to be sized to the maximum volume of data activity at any given time, rather than the average volume, leaving a lot of bandwidth unused.

In addition, businesses expect tighter and tighter RPO and RTO, which puts a heavier burden on existing WAN infrastructure and often creates a bottleneck to improving data replication performance and reliability over the WAN. Dedicated WAN replication links are becoming less common, so important replication traffic often competes for bandwidth with less important types of traffic.

The key characteristics that affect WAN performance include latency, packet loss rates, congestion, and amount of available bandwidth. Unfortunately, these characteristics can change over time and adversely affect the performance of what was originally a sound DR plan. In addition, when the DR application shares the WAN with non-replication traffic, file transfers, and other application traffic, the RPOs and RTOs that were previously attainable can become out of reach. Many customers resign themselves to living with lower than desired performance. One fix often attempted is to replicate only the most critical data and therefore reduce the amount of data replicated. Another common solution is to lease additional bandwidth. Neither is ideal because they both either significantly increase business risk or costs.

1 http://www.f5.com/pdf/analyst-reports/forrester-apps.pdf

F5 WANJet® for EMC SRDF™

F5 Solution Brief

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Solution – WANJet WAN Optimization ApplianceThe F5 WANJet appliance is a high performance WAN optimization and traffic-shaping solution designed to improve the throughput performance of IP traffic over the WAN. It was designed for data center to data center replication where there are few connections and very high throughput requirements (for example, DS-3, OC-3, OC-12, OC-48, etc). WANJet is able to optimize the existing WAN thereby achieving significant performance gains without having to add any additional bandwidth.

WANJet is deployed symmetrically, meaning there is one device on each side of the WAN (see diagram below). For larger WAN links, or high availability scenarios, multiple WANJets can be used together on each side of the WAN. WANJet does not interfere with the applications, generating the TCP/IP traffic, and does not alter the data in any way.

S ourc e S ym m

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IP VPNMPLS

Frame RelayPoint to Point

GigaMANIP over DWDM

F5 Solution Brief

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There are five steps that WANJet goes through in order to accelerate and manage the traffic being sent through it: First, WANJet puts traffic through byte-level pattern matching. This is a similar concept to data de-duplication, and the goal is to avoid transmitting the same data twice. As traffic flows through the WANJets, they build up a library of seen bit patterns. These libraries are kept in synch between the two WANJets. In the event that the same byte pattern is seen on the sending WANJet, the sending WANJet will replace the byte pattern with a much smaller library reference. This library reference is recognized by the receiving WANJet, which then replaces the reference with the actual traffic. Thus the receiving array does not see any difference in the data itself. This is very different from file-level de-duplication, and much more efficient for replication scenarios that are not necessarily dealing at the file-level.

WANJet then puts traffic through Adaptive Compression. There are a wide variety of compression algorithms that have been developed during the last 20 years. Virtually all compression functions use these same algorithms. What is unique about WANJet compared to other WAN optimization products, is that it applies compression “adaptively,” has access to a number of algorithms, and uses different ones in different combinations depending on the particular data being sent at that time and the network conditions.

The third step involves using a number of techniques for optimizing the TCP/IP communication stream, including TCP window sizing to ensure that the back and forth chatter of TCP is optimized.

The fourth step sets the application Quality of Service (QoS) in the WANJet optimization policy (by port or IP address), which ensures that you have control over what traffic gets priority access to bandwidth in the event of congestion. WANJet can set the network Type-of-Service (ToS) bits per your defined policy to take advantage of optimization along the path in routers and switches.

The final step is the optional SSL encryption of traffic traveling over the WAN. This traffic is decrypted upon arrival at the receiving WANJet, and provides an extra layer of security.

There are numerous benefits that WANJet brings to data replication solutions like SRDF including:

n Accelerating replication cycles.

n Lowering RPO and RTO times.

n Reducing bandwidth utilization and expenses by up to 90%.2

n Minimizing susceptibility to performance variations caused by WAN conditions (for example, high latency or packet loss).

n Reducing overall host response times. This may enable synchronous replication if latency was previously too high to allow this.

n Reducing the tangible and intangible costs of troubleshooting performance.

n Gaining more control over WAN resources allocated to storage.

2 Based on actual customer deployments; results may vary.

F5 Solution Brief

OptimizedSRDFTCP Acceleration

Step 3Transmit more efficiently Control access to bandwidthReduce the amount of data sent over the wire

Transparent Data Reduction #2

(byte-level pattern matching)

Step 1

Transparent Data Reduction #1(compression)

Step 2

Optional QoS/BandwidthAllocation

Step 4

RawSRDF

Optional SSL Encryption

Step 5

F5 Solution Brief

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WANJet and EMC Symmetrix Remote Data FacilityF5’s WANJet helps improve the performance of the WAN, and operates with any TCP/IP over Ethernet traffic. Specifically, WANJet has been tested and approved by EMC’s E-Lab3 for SRDF/Asynchronous and SRDF/Data Mobility where the Symmetrix is using gigabit over Ethernet. The EMC E-Lab conducts the industry’s most rigorous, end-to-end interoperability testing, and their promise is to deliver the highest level of interoperability assurance, and they support every configuration they qualify. This rigorous testing of WANJet with SRDF ensures that customers can deploy WANJet safely, successfully, and quickly alongside their SRDF solutions.

Results of testing are available directly from EMC’s E-Lab, and a detailed deployment guide is available from F5.

In both the E-Lab and customer deployments WANJet has provided significant acceleration benefits to SRDF. With WANJet customers experience fewer network related performance problems, accelerate performance from their DR investment, improve RPO and RTO, and minimize bandwidth expenses. Ultimately, that boils down to less business risk and lower cost of insuring against those risks. Organizations can meet their SLA (for example, RPO/RTO) targets more easily, and within budget. That means less risk to equity investors as well.

3 http://www.emc.com/interoperability/

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Additional Information

EMC Information

EMC Select information: http://www.emc.com/partnersalliances/programs/select.jsp.

EMC Select catalog: http://www.emc.com/partnersalliances/programs/pdf/H1900_EMC_Select_catalog_ldv.pdf

EMC E-Lab information: http://www.emc.com/interoperability/

WANJet Information

WANJet datasheets, white papers, and customer case studies: http://www.f5.com/products/wanjet/.

WANJet for SRDF white paper: http://www.f5.com/pdf/white-papers/wanjet-emc-wp.pdf

WANJet in Data Replication Environments white paper: http://www.f5.com/pdf/white-papers/data-replication-wp.pdf

F5 Solution Brief