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ACS-8990/89200/89230 User's Manual
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The ACS-8990 can support the following RAID levels: 0, 1, 3, 5, 0+1, 30, 50 , NRAID and
JBOD.
Which is the right level for you? The answer depends on the application you use your RAID for.
RAID Level 0 offers high transfer rates, and is ideal for large blocks of data where speed is of
importance. Computer Aided Design, Graphics, Scientific Computing, Image and Multimedia
applications are all good examples. If one drive in a RAID 0 array fails however, the data on the
whole array is lost.
RAID Level 1 may be an appropriate choice if cost and performance are of significantly less
importance than fault tolerance and reliability.
RAID Level 0+1 offers a compromise between the reliability and tolerance of level 1 and the
high transfer rates provided by level 0.
RAID Level 3 is similar to the more commonly used level 5. Both offer a good level of fault
tolerance and overall system reliability at a reasonable cost for redundancy overhead.
RAID Level 30 offers a compromise between the reliability and tolerance of level 3 and the high
transfer rates provided by level 0.
RAID Level 5 arrays offer high I/O transaction rates, and are the ideal choice when used with
on-line transaction processing applications, such as those used in banks, insurance companies,
hospitals, and all manner of office environments. These applications typically perform large
numbers of concurrent requests, each of which makes a small number of disk accesses. If one
drive in a RAID 5 array fails, the lost data can be rebuilt from data on the functioning disks.
RAID Level 50 offers a compromise between the reliability and tolerance of level 5 and the high
transfer rates provided by level 0.
JBOD is a method of arranging multiple disks that is not technically a RAID at all. Under JBOD
("Just a Bunch of Disks") all disks are treated as a single independent volume JBOD providing
no fault tolerance, or performance improvements over the independent use of its constituent
drives.
NRAID (Non-RAID) combines the space of all physical disks and forms a large logical disk. The
space presented by the NRAID starts sequentially from the first member disk to the last
member disk without striping, mirroring, or parity. The capacity of the logical disk is the direct
sum of all physical hard disks .
This appendix provides a summary of the features of each RAID level to enable users with
differing requirements to makes the best choice.
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