Summary Of Raid Levels; Raid Terminology - Dell 6 series User Manual

Summary of RAID Levels

• RAID 0 uses disk striping to provide high data throughput, especially for
large files in an environment that requires no data redundancy.
• RAID 1 uses disk mirroring so that data written to one physical disk is
simultaneously written to another physical disk. RAID 1 is good for small
databases or other applications that require small capacity, but also require
complete data redundancy.
• RAID 5 uses disk striping and parity data across all physical disks
(distributed parity) to provide high data throughput and data redundancy,
especially for small random access.
• RAID 6 is an extension of RAID 5 and uses an additional parity block.
RAID 6 uses block-level striping with two parity blocks distributed across
all member disks. RAID 6 provides protection against double disk failures,
and failures while a single disk is rebuilding. If you are using only one array,
deploying RAID 6 is more effective than deploying a hot spare disk.
• RAID 10, a combination of RAID 0 and RAID 1, uses disk striping across
mirrored disks. It provides high data throughput and complete data
redundancy. RAID 10 can support up to eight spans, and up to 32 physical
disks per span.
• RAID 50, a combination of RAID 0 and RAID 5, uses distributed data
parity and disk striping and works best with data that requires high system
availability, high request rates, high data transfers, and medium to large
capacity.
• RAID 60 is a combination of RAID 6 and RAID 0, a RAID 0 array is striped
across RAID 6 elements. RAID 60 requires at least 8 disks.

RAID Terminology

Disk Striping
Disk striping allows you to write data across multiple physical disks instead of
just one physical disk. Disk striping involves partitioning each physical disk
storage space in stripes of the following sizes: 8 KB, 16 KB, 32 KB, 64 KB,
128 KB, 256 KB, 512 KB, and 1024 KB. These stripes are interleaved in a
repeated sequential manner. The part of the stripe on a single physical disk is
called a stripe element.
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Overview