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SAN Buying Guide

A SAN is a high-performance, dedicated device or network of devices designed to store data that can be rapidly accessed by connected servers. It moves storage resources off the common user network.

Storage Area Network (SAN) units are expandable so you can have multiple trays and get a very high capacity of storage. The drives are controlled by controllers in the SAN and these handle all the raid configurations. The SANs usually have dual controllers and dual PSUs for redundancy.

You can get SANs with 2.5" and 3.5" drives but you can't usually mix and match shelves. Large disks are ideal where capacity is required, and smaller disks are ideal for speed - with 15,000rpm 10,000rpm SAS disks falling into this form factor. Enterprise-level SSDs are usually in 2.5" form factor.

Storage-area networks are managed centrally, and Fibre Channel (FC) SANs have the reputation of being expensive, complex and difficult to manage. The emergence of iSCSI has reduced these challenges by encapsulating SCSI commands into IP packets for transmission over an Ethernet connection, rather than an FC connection. Instead of learning, building and managing two networks - an Ethernet local-area network (LAN) for user communication and an FC SAN for storage - an organization can now use its existing knowledge and infrastructure for both LANs and SANs.

Virtual SAN

A virtual storage-area network (VSAN) is a software-defined storage offering that is implemented on top of a hypervisor such as VMware ESXi or Microsoft Hyper-V. Virtual SANs yield a number of benefits such as ease of management and scalability. For the most part, VSANs are hardware-agnostic. As long as the storage hardware is recognized and supported by the hypervisor, the hardware can be used by the VSAN (although each vendor has its own requirements).

Unified SAN

Unified SAN is based around the concept of unified storage, which exposes file storage and block storage through a single device (usually a modified NAS appliance).