IBM DS8000 manual Naming, Storage complex, Storage unit, Storage facility image

4.1 Naming

It is important to understand the naming conventions used to describe DS8000 components and constructs in order to fully appreciate the discussion of RAS concepts.

Storage complex

This term describes a group of DS8000s managed by a single Management Console. A storage complex may consist of just a single DS8000 storage unit.

Storage unit

A storage unit consists of a single DS8000 (including expansion frames). If your organization has one DS8000, then you have a single storage complex that contains a single storage unit.

Storage facility image

In ESS 800 terms, a storage facility image (SFI) is the entire ESS 800. In a DS8000, an SFI is a union of two logical partitions (LPARs), one from each processor complex. Each LPAR hosts one server. The SFI would have control of one or more device adapter pairs and two or more disk enclosures. Sometimes an SFI might also be referred to as just a storage image.

Processor		Processor
complex 0		complex 1
server 0	Storage	server 1
	facility
	image 1
	LPARs

Figure 4-1 Single image mode

In Figure 4-1server 0 and server 1 create storage facility image 1.

Logical partitions and servers

In a DS8000, a server is effectively the software that uses a logical partition (an LPAR), and that has access to a percentage of the memory and processor resources available on a processor complex. At GA, this percentage will be either 50% (model 9A2) or 100% (model 921 or 922). In ESS 800 terms, a server is a cluster. So in an ESS 800 we had two servers and one storage facility image per storage unit. However, with a DS8000 we can create logical partitions (LPARs). This allows the creation of four servers, two on each processor complex. One server on each processor complex is used to form a storage image. If there are four servers, there are effectively two separate storage subsystems existing inside one DS8000 storage unit.

62DS8000 Series: Concepts and Architecture