IBM System storage DS6000 Series, Redbooks

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DS6000 Series: Concepts and Architecture
Figure 4-2 Array sites
Array sites
are the building blocks used to define
arrays.
4.2.2 Arrays
Arrays
are created from one or two
array sites.
Forming an array means defining it for a
specific RAID type.The supported RAID types are RAID-5 and RAID-10 (see 3.3.1, “RAID-5
overview” on page 52 and 3.3.2, “RAID-10 overview” on page 53). For each array site or for a
group of two array sites you can select a RAID type. The process of selecting the RAID type
for an array is also called
defining
an array.
According to the DS6000 sparing algorithm, up to two spares may be taken from the array
sites used to construct the array on each device interface (loop). See Chapter 5, “IBM
TotalStorage DS6000 model overview” on page 83 for more details.
Figure 4-3 on page 69 shows the creation of a RAID-5 array with one spare, also called a
6+P+S array (capacity of 6 DDMs for data, capacity of one DDM for parity, and a spare drive)
from two array sites. According to the RAID-5 rules, parity is distributed across all seven
drives in this example.
Also referring to Figure 4-3, on the right side the terms D1, D2, D3, and so on stand for the
set of data contained on one disk within a stripe on the array. If, for example, 1 GB of data is
written, it is distributed across all the disks of the array.
Array
Site 1
Array
Site 2
Switches
Loop 1 Loop 2