Logical

 

 

 

 

 

 

view:

Storage Facility image 1

Storage Facility image 2

virtual

 

RIO-G

 

 

RIO-G

 

Storage

LIC

LIC

LIC

LIC

I/O

I/O

 

I/O

 

I/O

Memory

 

Memory

Memory

 

Memory

Facility

Processor

 

Processor

Processor

 

Processor

images

 

 

LPAR Hypervisor

 

 

Physical

 

 

 

takes part of

 

 

takes part of

 

 

 

 

takes part of

view:

 

 

 

RIO-G

 

 

physical

 

 

 

 

 

 

 

I/O

I/O

 

 

storage

Memory

 

 

Memory

unit

Processor

 

 

 

Processor

 

 

 

 

Figure 5-1 Storage Facility virtualization

5.3 The abstraction layers for disk virtualization

In this chapter, when talking about virtualization, we are talking about the process of preparing a bunch of physical disk drives (DDMs) to be something that can be used from an operating system, which means we are talking about the creation of LUNs.

The DS8000 is populated with switched FC-AL disk drives that are mounted in disk enclosures. You order disk drives in groups of 16 drives of the same capacity and RPM. The disk drives can be accessed by a pair of device adapters. Each device adapter has four paths to the disk drives. The four paths provide two FC-AL device interfaces, each with two paths, such that either path can be used to communicate with any disk drive on that device interface (in other words, the paths are redundant). One device interface from each device adapter is connected to a set of FC-AL devices such that either device adapter has access to any disk drive through two independent switched fabrics (in other words, the device adapters and switches are redundant).

Each device adapter has four ports and since device adapters operate in pairs, there are eight ports or paths to the disk drives. All eight paths can operate concurrently and could access all disk drives on the attached fabric. In normal operation, however, disk drives are typically accessed by one device adapter. Which device adapter owns the disk is defined during the logical configuration process. This avoids any contention between the two device adapters for access to the disks.

Chapter 5. Virtualization concepts

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IBM DS8000 manual Abstraction layers for disk virtualization, Storage Facility virtualization