Tip

Integrate your SAN with hubs

When you are going to move some of your data and/or applications to a SAN, how do you go about it? If you already have one or more SANs in your outfit, then you know what to do. But what if you don't? This tip, excerpted from InformIT,

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talks about the easiest way to slide your new SAN into your infrastructure, so that you can have your SAN, and expand it, too.

The article on InformIT from which this tip is excerpted comes from The Essential Guide to Storage Area Networks, first edition, published by Prentice Hall.


The best way to integrate any new technology is to start small, master the technology, and grow. Start the SAN topology in a department with a managed hub connecting the existing server to the new SAN that connects either a RAID or a simple disk array. This will provide a low-cost entry with great flexibility that will be used as a building block for subsequent configurations. A reasonable first step is migrating Small Computer Systems Interface (SCSI) bus devices to the new Fibre Channel way of doing things. Attaching existing SCSI arrays to a protocol converter for Fibre can provide investment protection, improved management, and easy implementation. Even this initial stage of SAN will provide faster access to data, improved scalability, greater distance capability, and improved data availability. Hub implementation will greatly ease the ability to enable a LAN-free/SAN based backup and restore capability with the appropriate application software. This results in a backup procedure that minimizes its impact on the LAN by putting the backup traffic on the SAN.

The hub stage should then be repeated in different departments or facilities as learning improves and the procedures have been tailored to fit the particular installation environment. The end result is a series of SAN hubs installed throughout the enterprise providing improved access, reliability, and performance.

The hub phase is also known as the SCSI bus migration phase, and it will provide immediate benefits while positioning for subsequent implementations. The money and time spent implementing this phase will be leveraged because the next phase will incorporate the investment made.

After the initial hubs and the storage system management software have been installed, departments or other logical groups should be linked together. This phase is called the storage infrastructure phase. This phase provides the first glimpse into the broader benefits of the SAN, while still protecting the investment in the hub phase and providing a smooth learning curve to ensure that the enterprise gets the highest return on investment from each phase of the SAN implementation. Linking the hubs with a small switch allows the departmental hubs to be connected with a backup link for higher availability. If one of the primary links between departments has problems, the alternate link can be utilized to provide improved availability. Additionally, it will enable the long-distance connection, up to 10km between two nodes, which provides greater disaster tolerance.

The distance and department segmentation that are provided with a switch will allow the departments to share valuable storage resources and start to develop common management of the storage resource. One of the largest benefits of a SAN is the simple sharing of storage assets, disk arrays, and tape libraries. One significant problem with traditional captive storage architecture is ensuring consistent management of the data in distributed departments. The switch allows hubs to link together while maintaining logical separation, but with fast physical connection. The switch also allows more disaster-tolerant applications because the departmental storage can now be backed up remotely, improving the availability of important data in case of an emergency. The logical separation prevents problems in one department from spilling over to another department.


To read the article from which this tip comes, click over to InformIT. You have to register there, but the registration is free.

To learn more about The Essential Guide to Storage Area Networks, first edition, click here.


This was first published in November 2002

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