Datasheet

4
Technology Overview
Xsan
SAN Basics
Over the past decade, virtually every industry has experienced exponential growth in
storage requirements. Beyond a demand for capacity, organizations are increasingly
concerned with data protection, as well as near-instant and reliable access to mission-
critical files. Three basic types of storage networking architectures have emerged to
address these needs: directed-attached storage (DAS), network-attached storage (NAS),
and the storage area network (SAN).
To appreciate the benefits of Xsan, it’s helpful to understand the differences among
storage architectures and the advantages of a SAN file system.
DAS and NAS Architectures
Direct-attached storage (DAS)
In a DAS configuration, disk drives or storage systems are connected directly to a
server over SCSI or Fibre Channel. The host server formats the DAS using a compatible
disk file system, such as UFS or HFS+, and shares the storage with clients over Ethernet
using a network file system, such as AFP, SMB/CIFS, or NFS.
Limitations of DAS and NAS systems
DAS and NAS architectures suffer from the
same limitations, including:
• Single point of failure. The DAS host or
NAS appliance is the single point of access
to storage—and, potentially, a single point
of failure.
• Performance bottlenecks. Since all file
system requests must go through a single
workstation or server, performance bottle-
necks occur. These bottlenecks can be
magnified by Ethernet bandwidth limitations.
• Difficult scalability. In both scenarios,
scalability is limited by the number of storage
devices that can be attached to the server. It’s
also cumbersome to add disks or RAID arrays
to NAS or DAS systems.
Client systems
Ethernet LAN
File server
External storage
Fibre Channel or
SCSI interconnect
Performance bottleneck and
potential single point of failure.
Direct-Attached Storage