Modeling and analysis of IP storage protocols for time critical applications
In the current storage era, Fibre Channel (FC) protocol is used for high performance and reliability, providing different levels of service with 1Gbps to 4Gbps physical interfaces. FC transports Small Computer System Interface (SCSI) data, between storage devices. FC spans from 500 meters to 10 Kilometers [27, 28] using multimode, single mode fibers respectively, limiting the storage to a site or between two sites. In order to overcome this distance limitation and implementation costs, Fibre Channel over Internet Protocol (FCIP) and Internet Fiber Channel Protocol (iFCP) were introduced [30, 31]. FCIP tunnels the fibre channel frames over Internet between two fiber switches, with in the same network. iFCP is an IP Based gateway to gateway protocol, which interconnects different FC-SANs. Again, all these protocols are involved with fiber channels which increase the cost. iSCSI is a new IETF standardized protocol, which transports SCSI data over Internet. Advancements in Ethernet technologies from 1Gbps to 10 Gbps make iSCSI deployment to yield better results in terms of performance and can be very cost effective compared to FCIP and iFCP. Some of the widely used storage applications in the industry are archiving and mirroring, these applications are used for backup/recovery process in IT industry. Archiving is a process in which data is written to portable media such as optical disks or magnetic tapes. Mirroring is a process of data replicated on the remote disk. Mirroring can be done in two ways, synchronous and asynchronous. In synchronous mirroring, when ever there is an update with data, it is written to both local and remote disk at the same time. In asynchronous mirroring, data is updated periodically irrespective of the actual update. If iSCSI is used for remote mirroring, end users need to ensure the performance of iSCSI should meet the requirements of the application. Most of the studies proved deficient in considering some or the other aspects. In this research work, the author presents the modeling and analysis of iSCSI between two SAN Islands considering iSCSI level errors, which will enable the IT industry to use this model for their analyze before they actually deploy. Throughout the analysis, the author employs asynchronous mirroring between the SAN Islands. iSCSI level errors need to be considered when the SCSI data is on the Internet, which will seriously effect the performance of the application in real time. The prototype was analyzed using TCP/IP and UDP traffic with both dedicated links and Internet links. When iSCSI is used to interconnect different SAN islands, one should ensure its performance to meet the application requirements. The bandwidth management for time critical applications like synchronous and asynchronous mirroring is essential while analyzing performance on IP networks, for this the key operations of iSCSI like iSCSI read, iSCSI write were modeled. Also, the throughput under realistic traffic conditions varying different parameters like network types, round trip time, bandwidth and distance was modeled. Security is another important attribute which should be taken in to account while IP networks are involved. It is essential to consider security of data while block level data is being transferred between two storage islands using iSCSI. The errors processed by this protocol on the IP network were considered and suitable iSCSI error recovery procedures were analyzed.
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