IBM DS8000 manual Ranks, Creation of an array

Array

Site

Creation of an array

Data
Data	RAID
Data
Data	Array
Data
Data
Parity
Spare

D1	D7	D13 ...
D2	D8	D14 ...
D3	D9	D15 ...
D4	D10	D16 ...
D5	D11	P	...
D6	P	D17 ...
P	D12	D18 ...

Spare

Figure 5-4 Creation of an array

So, an array is formed using one array site, and while the array could be accessed by each adapter of the device adapter pair, it is managed by one device adapter. Which adapter and which server manages this array is be defined later in the configuration path.

5.3.3 Ranks

In the DS8000 virtualization hierarchy there is another logical construct, a rank.

When you define a new rank, its name is chosen by the DS Storage Manager, for example, R1, R2, or R3, and so on. You have to add an array to a rank.

Note: In the current DS8000 implementation, a rank is built using just one array.

The available space on each rank will be divided into extents. The extents are the building blocks of the logical volumes. An extent is striped across all disks of an array as shown in Figure 5-5 on page 89 and indicated by the small squares in Figure 5-6 on page 90.

The process of forming a rank does two things:

￿The array is formatted for either FB (open systems) or CKD (zSeries) data. This determines the size of the set of data contained on one disk within a stripe on the array.

￿The capacity of the array is subdivided into equal sized partitions, called extents. The extent size depends on the extent type, FB or CKD.

An FB rank has an extent size of 1 GB (where 1 GB equals 230 bytes).

People who work in the zSeries environment do not deal with gigabytes, instead they think of storage in metrics of the original 3390 volume sizes. A 3390 Model 3 is three times the size of

88DS8000 Series: Concepts and Architecture