Understanding the IBM TotalStorage Open Software Family

36 Understanding the IBM TotalStorage Open Software Family

In this book, we use the following terms:

Host Any server that is using storage and runs applications for

its clients.

Agent A hardware or software component installed on a host to

virtualize its view of storage or to execute a specific

storage management function for that particular host.

Server A component of the storage network that provides a

service to its clients. This can be a host server or a

metadata server.

Client Something requesting a service from a server. This can

be a client to an application on a host or a host when

requesting service from a virtualization server.

Controller A hardware or software component that controls access

and usage of the storage resources it manages.

Now to save you from total confusion, let us agree that client and server are

interchangeable terms and that the relationship is defined by the interaction at a

particular time. We will use illustrations to clarify these interactions and qualify

the terms, where appropriate.

1.6.3 Levels of virtualization

We will define the different levels at which virtualization can be achieved in a

storage network, as illustrated in Figure 1-11 on page 37.

Chapter 1. Understanding storage concepts 37

Figure 1-11 Virtualization levels

Server level

Abstraction at the server level is accomplished by the volume management of

the operating systems on the servers. Some operating systems, like OS/390®

with DFSMS, have a high level of abstraction, whereas others still present, to the

user, volumes that are directly related to physical disks. At first sight, increasing

the level of abstraction on the server seems well suited for environments without

storage networks, but this can be vitally important in storage networks too, if we

look at the security and sharing issues.

Fabric level

On the SAN Fabric level, virtualization can enable the independence of storage

pools from heterogeneous servers. A single management interface can be

implemented to manage disparate storage systems without impacting the

servers. Several approaches are possible, and we will go into more detail on this.

Storage level

At the storage device level, several virtualization techniques have already been

tried, ranging from striping and redundant array of independent disks (RAID) to

sophisticated volume management in the Enterprise Storage Server (ESS) or

SAN

Server Level

Fabric Level

Storage Level

UNIX / AIX / HP-UX / SUN Solaris

Linux Microsoft Windows

Meta-Data Server

ESS

FAStT