Asus M3A78-EMH HDMI User Manual download pdf (Page 101)

Chapter 6: Technology Background

RAID 1 – Mirror

When a logical drive is mirrored, identical data is written to a pair of physical

drives, while reads are performed in parallel. The reads are performed using

elevator seek and load balancing techniques where the workload is distributed in

the most efficient manner. Whichever drive is not busy and is positioned closer to

the data will be accessed first.

With RAID 1, if one physical drive fails or has errors, the other mirrored physical

drive continues to provide fault tolerance. Moreover, if a spare drive is present,

the spare drive will be used as the replacement drive and data will begin to be

mirrored to it from the remaining good drive.

Figure 2. RAID 1 mirrors identical data across to two physical drives

Due to the data redundancy of mirroring, the capacity of the logical drive equals

the size of the smallest physical drive. For example, two 100 GB physical drives

which have a combined capacity of 200 GB instead would have 100 GB of usable

storage when set up in a mirrored logical drive. Similar to RAID 0 striping, if

physical drives of different capacities are used, there will also be unused capacity

on the larger drive.

RAID 1 logical drives on the AMD SB6xx/SB7xx Controller consist of two

physical drives. You can create multiple RAID 1 logical drives on the same

Controller.

Data Mirror

physical drives

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Asus M3A78-EMH HDMI User Manual Page 101