Adaptec 2268300R Manuel D’Utilisation

Appendix B: Understanding RAID

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Understanding Drive Segments

A drive segment is a disk drive or portion of a disk drive that is used to create an array. A disk 
drive can include both RAID segments (segments that are part of an array) and available 
segments. Each segment can be part of only one logical device at a time. If a disk drive is not 
part of any logical device, the entire disk is an available segment.

Non-redundant Arrays (RAID 0)

An array with RAID 0 includes two or more disk drives and provides data striping, where data 
is distributed evenly across the disk drives in equal-sized sections. However, RAID 0 arrays do 
not maintain redundant data, so they offer no data protection. 

Compared to an equal-sized group of independent disks, a RAID 0 array provides improved I/O 
performance. 

Drive segment size is limited to the size of the smallest disk drive in the array. For instance, an 
array with two 250 GB disk drives and two 400 GB disk drives can create a RAID 0 drive 
segment of 250 GB, for a total of 1000 GB for the volume, as shown in this figure.

Disk Drive 1

Disk Drive 2

Disk Drive 3

Disk Drive 4

250 GB

250 GB

400 GB

400 GB

Drive Segment Size 
(Smallest Disk Drive)

Disk Drive 2

Disk Drive 3

Disk Drive 4

Disk Drive 1

1

5

...

997

2

6

...

998

3

7

...

999

4

8

... 1000

Unused Space = 150 GB

Disk Drives in Logical Drive

RAID 0 Logical Drive = 1000 GB

Unused Space = 150 GB