Part 1: When is a server a good SAN candidate?

A reader recently asked Chris Poelker the following question:

We are planning to install a SAN/NAS and we have about 400 servers. What criteria shall we apply to classify a server as a candidate for the SAN? What are the justifications for the criteria? What process is normally followed in such a case?

Here's Chris Poelker's detailed answer:

Great question, and an opportunity for me to use a blatant plug for my book "Storage Area Networks for Dummies", Chapter 1. The later chapters in the book go over this topic in more detail.

Here is an excerpt from Chapter 1 that I think you may find useful.

The SAN platforms:

The platforms are the servers that benefit from using a SAN. As I indicate earlier in this chapter, not all servers should be hooked up to a SAN. The operating system running on your server requires a driver. A driver is a small bit of software (drivers are discussed in Chapter 7) that enables the server talk to the disks in the SAN. Some operating-system platforms have these drivers available, some don't. You may need the latest version of your operating system to use a SAN because of a lack of driver support in earlier versions. For example, older versions of Windows NT, such as Windows NT 3.51, don't have SAN drivers available.

Most server platforms have drivers that allow them to be hooked up to a SAN environment. Whether doing so makes sense depends on the type of application running on it and the amount of disk storage that the server needs.

Here is a list of the minimum operating system versions required to include in a SAN:

* Microsoft Windows NT 4.0
* Microsoft Windows 2000
* Sun Solaris versions 2.6 through 2.8
* HP-UX version 10.2 and higher
* IBM AIX version 4.2 and higher
* Compaq Tru64 Unix version 4.0F and higher
* Compaq Open VMS version 7.2 and higher
* Novell Netware version 4.11 and higher
* SGI IRIX version 6.5 and higher
* Sequent DYNIX version 4.5 and above
* The various flavors of Linux
* IBM OS/390 Mainframe MVS, or Z/OS

Applications that benefit from a SAN:

Most applications running on a server would benefit from faster access to the disk drives that the application is trying to use. Using a SAN instead of disks inside the server not only makes disk access faster (SAN disk access is at light speed) but also makes managing those disks much easier.

You can use the following as a guideline when choosing which servers to hook up to the SAN.

* Any server-class computer running a high-performance application. By server class I mean anything with lots of memory (1GB or more) and a fast Intel Xeon or reduced instruction set computer (RISC) class processor. Not your normal desktop type PC.

* Any server-class computer with expanding disk storage needs. Using a SAN makes it easy to allocate more storage to a server without having to bring the server down to do it!

* Any database-type application server. Databases require very fast disk access. A SAN can provide this kind of fast disk access.