Striping methods
There are two methods for configuring the physical layout of the disk arrays:
• Vertical striping—the RAID array uses one physical drive from each disk enclosure.
• Horizontal striping—the RAID array uses multiple drives contained within one or more disk enclosures.
RAID levels
Controllers use RAID technology to group multiple disk drives together in larger logical units (LUNs). Key RAID methods
include the use of data striping, data mirroring, and parity error checking. Data striping improves speed by performing
virtual disk I/O with an entire group of physical disks at the same time. Mirroring provides data redundancy by storing
data and a copy of the data. Parity error checking provides automatic detection and correction if corruption of a physical
disk occurs.
Depending on the host environment, the following RAID levels are supported with this disk enclosure:
RAID 0
RAID 0 is optimized for I/O speed and eicient use of physical disk capacity, but provides no data redundancy.
RAID 1
RAID 1 is optimized for data redundancy and I/O speed, but uses the most physical disk space.
IMPORTANT: RAID 1 uses about 100% more physical disk space than RAID 0 and 70% more than RAID 5.
RAID 5
RAID 5 protects against failure of one drive (and failure of particular multiple drives) of data. RAID 5+0 is a nested
RAID method that uses RAID 0 striping across RAID 5 arrays.
RAID 6
RAID 6+0 allows administrators to split the RAID 6 storage across multiple external boxes. RAID 6+0 requires a
minimum of eight drives. RAID 6+0 is a nested RAID method that uses RAID 0 block-level striping across multiple
RAID 6 arrays with dual distributed parity. With the inclusion of dual parity, RAID 6+0 will tolerate the failure of two
disks in each spanned array without loss of data.
RAID 6 with Advance Data Guarding (ADG)
RAID 6 with ADG allocates the equivalent of two parity drives across multiple drives and allows simultaneous write
operations.
• Distributed Data Guarding (RAID 5): Allocates parity data across multiple drives and allows simultaneous write
operations.
• Drive Mirroring (RAID 1 and 1+0 Striped Mirroring): Allocates half of the drive array to data and the other half to
mirrored data, providing two copies of every file.
Each level uses a dierent combination of RAID methods that impact data redundancy, the amount of physical disk space
used, and I/O speed. After you create a LUN, you cannot change the RAID level.
The following table compares the dierent RAID levels:
RAID level
Data redundancy RAID method
RAID 0 None Striping
RAID 1 High Mirroring
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