D-Link DSN-4200 DSN Series SAN Arrays VMWare ESX Manual - Page 3
Executive Summary, Overview
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xStack Storage DSN-Series SAN Arrays VMware ESX 3.0.2 & 3.5 Executive Summary The xStack Storage Series iSCSI storage arrays from D-Link provide cost-effective, easy-todeploy shared storage solutions for applications like the VMware Infrastructure 3 server virtualization software. In this document the features and performance of the D-Link xStack Storage™ Series iSCSI storage arrays along with typical server systems are configured, instructions for use with VMware are given, and recommendations are made. Overview Server virtualization programs such as VMware run best when the datacenter or enterprise is organized into "farms" of servers that are connected to shared storage. By placing the virtual machines' virtual disks on storage area networks accessible to all the virtualized servers, the virtual machines can be migrated from one server to another within the farm for purposes of load balancing or failover. VMware Infrastructure 3 uses the VMotion live migration facility in its Distributed Resource Scheduling feature and provides a High Availability component which takes advantage of shared storage to quickly boot up a virtual machine on a different ESX server after the original ESX server fails. Shared storage is key to enabling VMotion because, when a virtual machine is migrated from one physical server to another, the virtual machine's virtual disk doesn't actually move. Only the virtual disk's ownership is changed while it continues to reside in the same place. The xStack Storage iSCSI storage arrays provide excellent performance, reliability and functionality and do not require specialized hardware and skills to set up and maintain. The Fibre Channel storage network starts with the fabric, which involves the use of FC host bus adapters (HBAs) in each server, connected by fiber cables to one or more FC switches, which in turn can network multiple storage arrays, each supporting a scalable number of high speed disk enclosures. An application's request for an input or output (IO) to storage originates as a SCSI (Small Computer System Interface) request, is packed into an FC packet by the FC HBA, and sent down the fiber cable to the FC switch for dispatch to the storage array that contains the requested data, similar to the way Internet Protocol (IP) packets are sent over Ethernet. For smaller IT shops or for those that are just starting out in the virtualization arena, an alternate shared storage paradigm is emerging that employs iSCSI (Internet SCSI) to connect the servers to the storage. In this case the communication between the server and the data storage uses standard Ethernet network interface cards (NICs), switches and cables. SCSI IO requests are packed into standard Internet protocol packets and routed to the iSCSI storage through Ethernet switches and routers. With iSCSI customers can leverage existing networking expertise and equipment to simplify their implementation of a storage network. Like Fibre Channel, iSCSI supports blocklevel data transmission for all applications, not just VMware. For security iSCSI provides CHAP authentication as well as IPSEC encryption. Servers can communicate with iSCSI storage using two methods. The first involves the use of an add-in card called an iSCSI hardware initiator or host bus adapter, analogous to the Fibre Channel HBA, which connects directly to the datacenter's Ethernet infrastructure. The second does the iSCSI conversion in software and sends the Ethernet packets through the standard Ethernet NIC. D-Link Systems, Inc. December 2, 2009 Page 3