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It is a challenge to maintain synchronized files across a distributed enterprise. In addition, it is costly to deploy and manage file servers in remote and branch offices. As a result, most enterprises prefer to centralize enterprise file servers.
It is difficult, however, to provide file access and transfer across a WAN, particularly in Microsoft® environments that leverage the “Common Internet File System” (CIFS) protocol. That is because CIFS is a particularly “chatty” protocol, which limits its performance across networks with high latency. Every time a file is transferred using CIFS, for example, it is methodically broken down into small blocks (4 KB to 64 KB). Each block is sent individually by the file server, requiring an acknowledgement by the client before the next set of information can be transferred.
On a LAN, this type of chattiness is not a problem. But, when limited bandwidth is coupled with high latency (100ms or greater), packet loss, and TCP delays, as is the case on many enterprise WANs, file services can slow to a crawl.
Data Deduplication using Network Memory
Silver Peak appliances use Network Memory to reduce the amount of repetitive information that is sent across the WAN when performing CIFS transfer and acknowledgements. Depending upon the type of file being transferred, this can lead to enormous performance improvements – over 50x in some instances (see charts below).
CIFS Performance improvements on a 1 Mb link with 100 ms latency and 0.05% loss
Silver Peak’s Network Memory is bi-directional. Once content traverses a WAN in one direction, the patterns are stored at each appliance. Future transfers in the opposite direction are immediately accelerated, enabling Silver Peak to offer amazing performance with exceptional scalability.
Network Acceleration Overcomes Latency
In the above charts, the Silver Peak solution demonstrates performance improvements on initial file transfers – prior to data being stored in the appliances. This is due to crossflow payload and header compression, as well as various techniques for TCP acceleration, including window and transaction size adjustments to compensate for poor performance on high latency links. Silver Peak also supports CIFS acceleration, including read-aheads and write-behinds to pipeline CIFS requests and the respective acknowledgements. This dramatically minimizes roundtrip delays when using CIFS over a WAN.
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