RAID stands for "Redundant Array of
Inexpensive Disks". This technology creates fast and reliable disk-drive
subsystems out of individual disks. RAID guards against disk failure. It
can also lead to a false sense of security.
RAID data recovery situations are treated as high priority recoveries.
We first provide an initial diagnosis and then create a raw image of all
data from accessible media if needed. Our analysis then determines the
potential data loss situation. Everesta Media thoroughly tests the
components and examines the computers internal diagnostics to determine
the extent of physical damage.
Many times we need to replace failed or damaged components to recover
crashed hard disks. We do so in a clean environment and use specialized
hardware and software tools to create the raw image.
Min.
# Drives
|
Description
|
Advantages
|
Disadvantages
|
|
RAID 0
|
|
|
Partitions divided into stripes and then
interleaved. |
Very high performance. |
Offers no redundancy. |
|
RAID 1
|
|
|
This is also referred to as
"disk mirroring". Two or more partitions, all of the same size, each
store an exact copy of all data, disk-block by disk-block.
|
Strong
protection against disk failure. High performance. |
Least efficient
in terms of storage. Can store no more data than a single partition. |
|
RAID 2
|
|
|
Combines RAID 0
(Data Striping) & RAID 1
(Data Mirroring). |
Highest performance and data
protection. Tolerates two or more disk failures. |
High redundancy
and thus higher cost. Requires a minimum of four drives.
|
|
RAID 2 & 3
|
|
Three
|
Seldom used
anymore. Made obsolete by modern disk technology. |
Similar to RAID
4. |
Requires all
drive spindles to be synchronized. |
|
RAID 4
|
|
|
Interleaves
stripes like RAID 0 and requires additional partition to store
parity. Parity is used to offer redundancy. RAID 4 is not widely
used. |
Supports data
striping of multiple read requests. |
Does not offer
the read performance of mirroring and offers considerably degraded
write performance. |
|
RAID 5
|
|
|
Employs block
level data striping with distributed parity . Avoids
write-bottleneck of RAID-4 by alternately storing the parity stripes
on each of the drives. |
Very high performance and data protection. Offers
protection against single drive failure. Offers far more storage
capacity when used with three or more drives. |
Read and write
performance is still not as good as mirroring. High redundancy means
higher cost. |
