The Basics of San Implementation

The Basics of SAN Implementation, Part II

August 7, 2003

By John Vacca

Most of the attention on SANs has focused on the performance benefits of a dedicated gigabit network that relieves conventional LANs of data movement loads. But, from a more holistic perspective, SANs will provide other significant advantages such as improved storage implementation, manageability, more reliable and flexible backup operations, and shared storage resources among multiple servers.

For peak demand periods, SAN-based implementations offer the ability to allocate additional resources to priority applications and servers. While server re-allocation is possible without SANs, such an approach is far less useful as storage resources cannot be shared. A powerful combination is dynamic server allocation with the ability to add or change storage resources without pre-determination.

One of the most attractive features of SAN implementation technology is its impact on standard network operations. The heavy overhead that conventional storage architectures place on LANs and network file servers is eliminated by relocating storage resources to an independent network.

With the preceding in mind, this article continues the SAN implementation theme presented in Part I, by briefly discussing other SAN implementation topics with regards to backups, clusters, appliances and database applications. Let's look at backups first.

SAN Backup Implementation

Backup operations, typically CPU intensive processes, will be completely removed from the servers. Faster, more reliable backup operations are a key component of SAN implementation. Indeed, the first generation of significant SAN-based applications will be built around a new generation of backup technologies such as:

• LAN-Free Backup.

• Server-Free Backup.

• Zero Backup Window.

• Multiple Small/Medium Libraries Versus One Large Library.

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The Basics of SAN Implementation, Part II

August 7, 2003

By John Vacca

LAN-Free Backup

Enterprise storage resources reside on an independent gigabit-speed network in a SAN implementation. All data movement occurs over this high-speed dedicated network and not a standard Ethernet LAN. The effect of SAN-based, LAN-free backup is an immediate improvement in LAN performance.

LAN-free backup technology gives multiple servers access to a single tape library connected to the SAN. Rather than the conventional Ethernet LAN, all backup operations are now routed through the gigabit-speed Fibre Channel SAN.

A new generation of SAN-aware backup software supports this architecture. In order to share tape libraries and eliminate data movement over the LAN, the backup software, being SAN-aware, coordinates between servers to allocate tape library resources. The first widely deployed storage management application to emerge on Storage Area Networks is likely to be LAN-free backup.

Server-free Backup

Server-free backup takes the LAN-free backup concept a step further. Not only are all backup operations relocated from the LAN to the SAN, but by enabling direct data movement between SAN devices, SAN bandwidth is maximized. In the case of backup, this means that the data moves directly from Redundant Array of Independent Disks (RAID) disk storage to the tape library; and, thus removes the server bottleneck.

Server-free backup leverages two key technical developments: the small computer system interface-3 (SCSI-3) block copy command (also known as third-party copy) and the Network Data Management Protocol (NDMP)-compliant software to manage communications between the server and the tape library. Also, for this application, the term "server-free" backup is actually somewhat of a misnomer. By using the NDMP to manage communications between the SAN storage devices, the server still plays a role in the backup operation and ensures that the backups are completed successfully. However, as in traditional backup operations, server intervention is minimized and all data is sent directly over the SAN and not via the server. This significantly increases performance, while improving the reliability of automated backup processes. As data moves