AIX > Storage > Servers

AIX EXTRA: Booting from the SAN

In the late 1990s, the SAN entered the data center environment. It enabled unprecedented performance, availability and recoverability of critical business systems by providing access to enterprise-class storage array technologies connected to the information systems used by businesses.

When SAN-based storage was first introduced in the data center, it was only used for the application data. OSs and, in many cases, applications themselves were still stored on disks directly attached to the host via SCSI or other directly attached disk channel technologies.

The use of SAN-based storage provided IT organizations with a number of exciting features beyond the host-based RAID technologies (see Figure 1). These features include the ability to rapidly copy the data in enterprise storage subsystems to another set of disks within the subsystem for protection, data migration, application data sharing and system testing. Another feature is the ability for SAN-based data to be backed up directly to SAN-attached tape subsystems so data managers don't need to use precious LAN or system resources to protect their environment from data loss. Enterprise storage systems provided IT with the ability to flash copy data to another part of the array so that database backups can be performed with little or no application downtime. In many environments, data volumes are replicated to remote locations, enabling rapid IT service recovery in the event of a primary data center loss.

These and many more features have resulted in the rapid adoption of SAN technologies by most medium and large businesses in recent years. IDC forecasts SAN storage to grow by as much as 66 percent annually.

The Next Step ... Booting from the SAN
IT organizations are employing many strategies to improve the efficiency of their operations (see
Figure 2). These include:

  • Increasing processor density by using the IBM BladeCenter.
  • Using logical partitions to deploy many system instances from a single platform.
  • Creating logical disks on SANs that more closely fit the storage requirements of the systems.

These strategies contribute to the need to separate the spinning disk resources from the processor and memory resources of the computer. Historically, the separation of processor from disk was accomplished by booting the computer from a server across the Ethernet. However, the Ethernet network introduces a performance limitation on the server and the amount of time it takes to boot contemporary OSs is prohibitive.


Jim Rice is the Principal IT Architecture Consultant for MSI Systems Integrators. Jim can be reached at

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