Striped Disk Array
striping, data is divided across multiple disks (or
spindles). Data is broken down into blocks, and each block
is written to a separate disk. The workload is reduced for
all disks, helping to accelerate data delivery times. RAID-0
helps make disks more responsive, especially for e-mail,
database, and Internet applications. RAID-0 requires at
least two hard disks to implement.
improved performance by spreading the I/O load across many
disks. Easy to implement.
offers NO data protection. Should not be used for critical
is achieved through what is called disk mirroring, and is
done to ensure data reliability. The same data is copied and
stored on different disks. If one disk fails, the data is
available somewhere else in the array and can be easily
restored. Mirroring not only creates redundant data for high
availability, but keeps critical applications running as
performance for reading data, with the same write
performance as a single disk. 100 percent data redundancy
means there is no data rebuild in case of a disk failure -
simply copy the data from the remaining disk in the pair.
use of disk capacity - subsequently has the highest overhead
of all RAID types (100 percent).
Striping with Parity
-5 maintains data redundancy through a technique called
parity checking. As data is striped across multiple disks,
parity bit data is included and also distributed among all
the disks in the array. Parity is used to maintain data
integrity and rebuild lost data in case of a disk failure.
If one disk in the array fails, the missing data can be
reconstructed from the remaining parity bits on the
surviving disks. A RAID-5 configuration requires at least
efficient use of disk capacity of all the redundant RAID
configurations. Maintains good read-write performance.
failure can impact throughput rates. Reconstructing
information after a disk failure takes longer than with a
Striping of Mirrored Arrays
is a combination of RAID-1 and RAID-0. This configuration
requires at least four disks, and offers the best
performance, protection, and capacity of all the RAID
levels. RAID-10 consists of pairs of mirrored disks whose
data is striped across the entire array. In many cases,
RAID-10 can sustain multiple simultaneous disk failures
making it less susceptible to downtime. It has the highest
probability of no data loss.
redundancy as RAID-1 (mirroring). Best choice for data
be expensive, due to the mirrored disk array.
Striping of Distributed Parity Arrays
is a combination of RAID-5 and RAID-0. This configuration
stripes data with parity across each RAID-5 subset of disks.
Each RAID-5 subset requires three hard disks. RAID-50
provides a higher degree of fault tolerance since one disk
per subset may fail without data loss. Since the parity bits
are distributed across the RAID-5 subsets, data rebuild
speed is increased.
degree of fault tolerance. Potential for faster data read
failure impacts throughput. Reconstruction of information
after a disk failure takes longer than with a mirrored