The Internet SCSI (iSCSI) Protocol provide a method of transporting traditional SCSI commands, data and status messages over standard TCP/IP networks. iSCSI offers a simple, cost-effective, standards-based way for even enterprises with modest budgets to deploy networked storage and gain the advantages of block-level storage consolidation.




 iSCSI boot allows administrators to boot server operating system over an iSCSI-based storage area network (SAN), helping simplify both server management and the creation, distribution and maintenance of server image.   

Networked Storage in the Data Center

Using servers on a network to store data is not a new concept, nor is booting a server from a network. Network Attached Storage (NAS) has existed since the introduction of Network File System (NFS) more than two decades ago.

NAS uses file-level protocols that abstract the underlying drive file system to provide networked storage such as shred drives in Linux or Unix Operating System using NFS or in the Microsoft Windows OS using Common Internet File System (CIFS). Although NAS is well suited for file sharing, it does not provide block-based functionality, which includes the ability to boot an OS.

Technologies such as Preboot Execution Environment  (PXE), Remote Program Load (RPL), and Bootstrap Protocol  (BOOTP), which have existed for years, are the current mechanisms for booting directly from a network. Although the system can be booted from a combination of NAS and PXE, BOOTP, and RPL, configuring system to do so is not a simple matter and may restrict system performance or capabilities.

The introduction of SANs provided block-level storage over a network, allowing shared resources to store application data from multiple servers and thereby helping increase storage utilization while reducing the number of devices for administrators to back up and manage. In this configuration, the file system appears to be present on a local Direct Attach Storage (DAS) disk within the server, but actually exists on a SAN array.

SAN technologies such as iSCSI help significantly simplify booting an OS from a network by providing the OS with low-level access to the storage device, which allow native file system access and the user of standard OS disk utilities.

Networked storage system such as NAS and SANs allow organizations to easily divide and share highly available pools of storage among groups of users, helping to meet applications increasing storage needs. These types of storage enable increased utilization, scalability and simplified backup solutions while helping increase data availability. Multiple enterprise requirements contribute to the need for networked storage:


Efficient Management: Consolidate the networked storage allows administrator to manage a single pool of central storage resources, rather than disparate, unconnected storage systems. Consolidation can also provide benefits such as reduced total cost of ownership and easy retargeting of servers, helping create a dynamic, scalable data center.

Regulatory compliance: Government regulations such as the Sarbanes-Oxley Act and Health Insurance Portability and Accountability Act (HIPAA) have increased enterprise documentation, auditing requirements, and data security.  With Networked storage, it can help ease the task of complying with these regulations.

High availability and robust disaster recovery: Networked storage supports high levels of availability while helping simplify disaster recovery, backup, and redundancy systems.


Advantages of iSCSI SAN Storage

Interoperability: Utilizing standardized networking technologies helps ensure interoperability between SAN components.

Reduced learning curve: Standard TCP/IP and Ethernet components are typically familiar to IT staff, helping reduce training, administrative and maintenance costs.

Flexibility: iSCSI supports a wide range of Ethernet network topologies, which can take advantages of the routing capabilities inherent in the IP protocol. In Additional, as a routable networked storage system, am iSCSI-SAN storage can be used over the Internet and across the enterprise.

Virtual LAN (VLAN) support: VLANs help isolate network and storage traffic and support quality-of-service protocols on Ethernet.

iSCSI boot allows a server to boot an OS over a SAN Storage, helping  eliminate the need for local disk storage, to enhance the system reliability and simplifying administrator workloads by centralizing the creation, and maintenance of server images.

As the use of SANs continues to grow, and the advantages of moving from local storage to centrally managed networked arrays become increasingly important, network boot solution such as iSCSI boot should become a common feature of enterprise data centers. Deploying this solution can help enterprises of all size realize the advantages of iSCSI based network storage while helping simplify management and reduce total cost of ownership.