Perfomance analysis and optimization of flow controlin SAN extension based on WDM

摘要

Fibre Channel (FC)becomes the main storage protocol of SAN(Storage Area Network).Enterprises areincreasingly deploying FC-SANs in their data central. In order to mitigate the risk of losing data, more andmore enterprises are increasingly adopting storage extension technologies based on WDM (WavelengthDivision Multiplexing) to replicate their business critical data to a secondary site. Storage Extension based on WDM makes use of the flow control mechanism based on Credit ,it offersimmediate access to the full link bandwidth without a ramp-up time ,but the updating frequency of Creditsand the throughput of storage extension are limited by the long extension distances. Adding the receivermemory can remove those limitations ,but it also brings about the long queuing time. In this paper, a Petri-Net model of FC flow control protocol is constructed to analysis the relativedegree between the storage extension performance with bandwidth , distance and initial number of Credit.Meanwhile, a new integrative flow control mechanism for storage extension based on WDM is proposed, it isconsists of three flow control loop A,B and C. A is deployed between FC sender and WDM ingress gateway,B takes affection on the WDM ingress gateway and WDM engress gateway, C works among WDM engressgateway and FC receiver, and the three flow control loop are integrated by the buffer utilization of ingress andengress gateway. Theoretical analysis and simulation result show that the new flow control method caneffectively remove distance limitation and allow data traffic to flow at maximum throughput without addingqueuing latency. The new flow control method is implemented in WDM gateway , it is transparent for FCprotocol and can provide a good compatibility .