Building and Using a SAN (Part II)

W. Curtis Preston

Editor's Note: We inadvertently omitted Figure 1 from Part I of Curtis Preston's article in the May issue. However, the same Figure 1 appears in this article, and the entire previous article can be read on the Sys Admin Web site. We regret any inconvenience.

In Part I of Building and Using a SAN (Sys Admin, May 2001), I talked about the three main areas of functionality that SANs make possible:

• Offline storage consolidation -- Offline storage consolidation is simply another way to say that you can share a tape library via the SAN. Tape drives are dynamically allocated to the servers that need them.

• Online storage consolidation -- When you move from discrete disks behind individual servers to putting all of your storage on the SAN, you have consolidated your online storage. This adds quite a bit of manageability and backup and recovery functionality. In the last issue, I only covered the administrative manageability issues. In this issue, I will cover the ways that online storage consolidation make backups easier.

• Truly highly available systems -- Although highly available systems are an entirely different discipline, I also wanted to cover how SANs make it easier to build truly highly available systems.

I will continue the discussion about building and using a SAN by examining the ways that online storage consolidation makes backups easier. I will then examine high-availability systems, followed by an overview of what's involved in building a SAN. See Figure 1 for an example of a SAN.

Online Storage Consolidation

Now that we've consolidated all of our online storage onto the SAN, what about backups? There are two very interesting possibilities that online storage consolidation facilitates.