Host vs servers in open systems storage – Randy Kerns on Storage Soup Blog

By Randy Kerns, Monday, January 24th 2011

Analyst Blogs

While working on a product analysis for the recently launched EMC VNX multiprotocol storage systems, I picked up on something I’ve also seen in other recent vendor presentations.

I’m seeing the word host commonly used to refer to the computing element that storage connects to, either directly or through a SAN. The word host takes me back to the mainframe terminology that has been around for so long.

The mainframe world has an entire lexicon of terms that are different than those used in the open systems world. A while back I made a list that translated the terms between mainframe and open systems for a storage systems class I was teaching. That list became popular and many people asked for a copy.

In open systems, people used the term servers instead of hosts. Now I’m seeing vendors use the term host in documentation and presentations for open systems. There are two reasons for this:

First, vendors generally define a host as a server running an application. This seems to be the most common sense definition. Second, the word server is really getting a broader meaning today. There are a number of reasons for this, specifically in the storage systems world.

With many storage solutions today, the storage function is really an application running on a standard server. It is a special application, usually with specific hardware requirements. It is often referred to as a server with the storage application. These systems may be characterized as appliances or even a software package that can be deployed on a server. This usage clouds the meaning of the term server, and requires a further explanation to determine which server is being referred to.

The standard client/server model that once defined open systems may no longer easily map to the definitions used where a server is running an application and has storage attached to the server. So when referring to a server running an application and storage that is critical to the operation, the term host can make it clearer. And, I suspect, that’s the main reason we’re seeing the term used that way so often now.

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