|
In many instances, the "weak link" in data replication can be traced to the Wide Area Network (WAN) that is used to connect different disaster recovery locations. Limited bandwidth, high latency, and packet loss are some of the WAN characteristics that can slow data replication processes to a crawl, or prevent them from happening entirely.
Under normal circumstances the amount of data collected can be easily sent across the WAN link, enabling the replication process to start and end based on defined minimum cycle time. However, during peak workload periods the amount of writes coming into the source device (Symmetrix or CLARiiON) may exceed the WAN link bandwidth. When this occurs, new data is collected until the last cycle has been successfully received on the other end, resulting in extra big cycle times and transfer delays across the WAN. This ultimately causes the replication process to fall behind established Recovery Point Objectives (RPO).
Silver Peak's WAN acceleration solution helps to address this issue by enabling more data to be transferred in less time. NX appliances prevent transfer times from falling behind cycle times and eliminate the need to spend a significant amount of money on WAN bandwidth to accommodate peak workloads. As a result, the combined EMC/Silver Peak solution is essential for enterprises with stringent business continuity objectives.
Silver Peak provides a robust WAN optimization solution that typically delivers a 6x-10x performance improvement in SRDF/A environments.
- Maximize WAN efficiency / improve data transfer times.
Silver Peak’s Network Memory recognizes repetitive information and sends a pointer to deliver the information locally, a concept known as data reduction. This is analogous to applying delta set technology at the network (i.e. WAN) layer. Because pattern matches can be made across all traffic types and with byte-level granularity, Network Memory can reduce over 85% of SRDF/A and MirrorView/A traffic across the WAN.
In addition, Silver Peak leverages advanced compression techniques to further reduce the amount of WAN bandwidth required for backup and replication. These techniques work in both directions of a WAN link, improving the backup/replication process while ensuring that the WAN can efficiently handle a restore if needed. By providing compression within the acceleration appliance, this functionality can be offloaded from the host replication server, ensuring better scalability and performance. In addition, significant performance improvement can be provided even when non-repetitive information is sent across the WAN.
- Latency mitigation.
SRDF and MirrorView leverage the Transport Control Protocol (TCP) for transport. As a result, delta set transfers are subject to the latency issues that often accompany this protocol. Silver Peak helps to overcome these issues by leveraging a variety of TCP acceleration techniques, including selective acknowledgements, high speed TCP, and increased TCP window sizes.
- Packet reordering.
Silver Peak adds sequence numbers on transmitted packets that are used to reorder packets on the far end of a WAN link in the event that the packets are received out-of-order. This is done prior to data being sent to the Symmetrix or CLARiiON device on the far end, and completely transparently to the SRDF and MirrorView processes.
- Reduce packet loss and delivery errors.
Silver Peak reduces the impact of both packet loss and jitter that occurs when router links are oversubscribed. This is handled via adaptive Forward Error Correction (FEC), a technology that is used to reconstitute lost packets at the far end of a WAN link, avoiding delays that come with multiple-round-trip retransmissions. The Silver Peak solution dynamically adjusts the FEC overhead in response to changing link conditions for maximum effectiveness in environments with high packet loss.
- Quality of Service.
Application level QoS can be used to ensure that replication services receive higher priority than other traffic, and that the appropriate bandwidth is always available for data management applications. This is particularly useful when target devices are not located in a dedicated disaster recovery site and a variety of business applications are vying for the same shared WAN bandwidth.
When Silver Peak is deployed with EMC SRDF/A and MirrorView/A, enterprises can better achieve their desired RTO and RPO, while maximizing investments in data protection, storage and networking infrastructure. The Silver Peak solution is particularly well-suited for high capacity WAN links (30 Mbps and higher) and environments with strict security guidelines, making it a nice complement to EMC’s target DMX and CLARiiON customer environments.
|
