AMCC 9590SE-4ME User Manual

Understanding RAID Levels and Concepts

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RAID 1 provides fault tolerance and a speed advantage over non-RAID disks. 
Also known as a mirrored array. Mirroring is done on pairs of drives. 
Mirrored disk arrays write the same data to two different drives using RAID 1 
algorithms (see Figure 2). This gives your system fault tolerance by 
preserving the data on one drive if the other drive fails. Fault tolerance is a 
basic requirement for critical systems like web and database servers.

3ware uses a patented technology, TwinStor®, on RAID 1 arrays for 
improved performance during sequential read operations. With TwinStor 
technology, read performance is twice the speed of a single drive during 
sequential read operation.

The adaptive algorithms in TwinStor technology boost performance by 
distinguishing between random and sequential read requests. For the 
sequential requests generated when accessing large files, both drives are used, 
with the heads simultaneously reading alternating sections of the file. For the 
smaller random transactions, the data is read from a single optimal drive head. 

                                      

 

RAID 5 provides performance, fault tolerance, high capacity, and storage 
efficiency. Requires a minimum of three drives. Combines striping data with 
parity (exclusive OR) to restore data in case of a drive failure.

Parity information is distributed across all drives rather than being 
concentrated on a single disk (see Figure 3). This avoids throughput loss due 
to contention for the parity drive.