User guide

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Creating RAID Groups
Redundant Array of Independent Disks (RAID) technology allows one or more disks to be combined into a
logical volume, which provides greater performance and/or protection than standard disk drives. These
volumes, known as RAID Groups, appear like regular disk drives to the operating system and can be
partitioned, formatted and used just like any other disk. The RAID complexity is hidden within the driver.
Note: The maximum allowable size of a RAID group that can be created by the SATARAID5
Manager is 144,115,188,075,855,872 bytes (which represents 2
48
bit addressability). However,
some Linux platforms may limit the maximum size of a volume to 2TB, so the largest allowable size
of a RAID group is 2,199,023,255,552 bytes.
RAID Levels
There are several methods of combining disks, each with its own advantages and disadvantages. Each
method is referred to as a RAID “level,” such as RAID 1 or RAID 5. The details of each level are
summarized below and detailed in the following sections.
RAID Level Advantages Disadvantages
RAID 0 High performance, low cost. No data protection.
RAID 1 Excellent data protection. High cost.
RAID 5
Good data protection, good value.
Performance degradation on
writes.
RAID 10
High performance, excellent data
protection.
High cost.
Concatenated
Good performance, low cost, large volume
size.
No data protection.
JBOD Same as single disk. Same as single disk.
Disk Striping (RAID 0)
Striping is a performance-oriented, non-redundant data mapping technique. While Striping is discussed as a
RAID Group type, it is does not provide any fault tolerance. With modern SATA and ATA bus mastering
technology, multiple I/O operations can be performed in parallel, enhancing data throughput. Striping arrays
use multiple disks to form a larger virtual disk. The figure below illustrates a three-disk stripe set. Stripe one is
written to disk one, stripe two to disk two, and so forth. RAID 0 sets can include two, three, four or five drives.
If the sizes of the disk segments are different, the smallest disk segment will limit the overall size of the RAID
Group.
Stripe 0
Stripe 1 Stripe 2
Stripe 3
Stripe 4 Stripe 5
Stripe 6
Stripe 9
Stripe 7
Stripe 10
Stripe 8
Stripe 11