Книга: Mastering VMware® Infrastructure3

Understanding a Storage Area Network

Understanding a Storage Area Network

A storage area network (SAN) is a communication network designed to handle the block-level transfer of data between a storage device and the requesting servers or hosts. The block-level transfer of data makes for highly efficient and highly specialized network communication that enables the reliable, low-latency transfer of large amounts of data with minimal server overhead. 

A SAN consists of several components that direct and manage the flow of data across the dedicated network. These components reside in one of three segments on the SAN:

? The hosts accessing the storage

? The network across which traffic runs

? The storage

The concepts of a storage area network have long revolved around using a Fibre Channel protocol for communication among nodes connected to the network. However, recently the quick adoption of iSCSI storage area networks has introduced a strong competitor to its fibre channel predecessor. Whereas fibre channel storage networks use the Fibre Channel Protocol (FCP) for communication among nodes, iSCSI provides a similar block-level data transfer over standard IP networks.

As your virtualization career moves forward, you will, at some point, most certainly be in a position where you must understand and differentiate between the two most popular SAN architectures today: Fibre Channel and iSCSI. Both architectures offer significant benefits in the areas of reliability, redundancy, scalability, performance, and security. Incorporating a shared storage back-end helps eliminate many of the network failure issues that administrators find themselves constantly fixing. ESX Server with a back-end SAN offers:

? Automatic failover and multipathing at the host bus adapter (HBA) and storage port

? A high-performance file system in VMFS-3

? VMotion, Distributed Resource Scheduler (DRS), and High Availability (HA)

? Support for Microsoft Cluster Services (MSCS)

? VMware Consolidate Backup (VCB)

SAN devices offer additional benefits in the areas of storage replication and mirroring. Using third-party software, you can replicate or mirror the data on your LUNs to other LUNs on the same or even different storage devices. This feature offers administrators great possibilities in the areas of disaster recovery and business continuity.

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