Adaptec 1220SA Manual De Usuario

Appendix B: Understanding RAID

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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 the following figure.

RAID 1 Arrays

A RAID 1 array is built from two disk drives, where one disk drive is a mirror of the other (the 
same data is stored on each disk drive). Compared to independent disk drives, RAID 1 arrays 
provide improved performance, with twice the read rate and an equal write rate of single disks. 
However, capacity is only 50 percent of independent disk drives.

If the RAID 1 array is built from different-sized disk drives, the free space, drive segment size is 
the size of the smaller disk drive, as shown in the following figure.

RAID 10 Arrays

A RAID 10 array is built from two or more equal-sized RAID 1 arrays. Adaptec RAID 
controllers support a maximum number of 48 disk drives in a RAID 10 array. 

Data in a RAID 10 array is both striped and mirrored. Mirroring provides data protection, and 
striping improves performance.

Disk Drive 1

Disk Drive 2

Disk Drive 3

Disk Drive 4

250 GB

250 GB

400 GB

400 GB

Disk Drive 1

Disk Drive 2

Disk Drive 3

Disk Drive 4

1

2

3

4

Not Used

Not Used

5

6

7

8

1000

999

998

997

...

...

...

...

Unused Space: 150 GB

Unused Space: 150 GB

Drive Segment Size (Smallest Disk Drive)

Disk Drive 1

Disk Drive 2

250 GB

400 GB

Disk Drive 1

Disk Drive 2

Not Used

Unused Space: 150 GB

1 – 250

1 – 250

Drive Segment Size (Smaller Disk Drive)