RAID 0 – Striping (Striped Disk Array without Fault tolerance)
It is the Stripped Disk Array with
no fault tolerance and it requires at least 2 drives
To be implemented. Due to no
redundancy feature, RAID 0 is considered to be the
Lowest ranked RAID level. Striped
data mapping technique is implemented for
High performance at low cost. The
I/O performance is also improved as it is loaded across many channels.
Recommended Applications
Video production and editing
Image editing
Pre-press applications
Any application requiring high
bandwidth
RAID 1 – Mirroring (Mirroring & Duplexing)
It is the Mirroring it is provide
high performance. RAID 1 controller is able to perform 2 separate parallel
reads or writes per mirrored pair. It also requires at least 2 drives to
implement a non-redundant disk array. High level of availability, access and
reliability can be achieved by entry-level RAID 1 array. With full redundancy
feature available, need of readability is almost negligible. Controller
configurations and Storage subsystem design is the easiest and simplest amongst
all RAID levels.
Disadvantages
Typically the RAID function is done
by system software, loading the CPU/Server and possible degrading throughput at
high activity levels. Hardware implementation is strongly recommended
May not support hot swap of failed
disk when implemented “software”
Recommended Applications
Accounting
Payroll
Financial
Any application requiring very high
availability
RAID 2 (ECC error correcting code) (Hamming Code ECC)
It is the combination of Inherently
Parallel Mapping and Protection RAID array.
It's also known as ECC RAID because
each data word bit is written to data disk
Which is verified for correct data
or correct disk error when the RAID disk is read.
Due to special disk features
required, RAID 2 is not very popular since ECC is embedded in almost all modern
disk drives.
Disadvantages
Very high ratio of ECC disks to
data disks with smaller word sizes – inefficient
Entry level cost very high –
requires very high transfer rate requirement to justify
Transaction rate is equal to that
of a single disk at best (with spindle synchronization)
No commercial implementations exist
/ not commercially visible.
RAID LEVEL 3 (Parallel Transfer with Parity)
At least 3 drives we need to
implementation in this raid level. Can be used single user environments which
access long sequential records to Speed up data transfer. However raid-3 does
not allow multiple I/O operation
We can use this raid level for
image editing, pre press applications.
Disadvantages
Transaction rate equal to that of a
single disk drive at best (if spindles are synchronized)
Controller design is fairly complex
Very difficult and resource
intensive to do as a "software" RAID
Recommended Applications
Video Production and live streaming
Image Editing
Video Editing
Prepress Applications
Any application requiring high throughput
RAID Level 4: Independent
Data Disk with Shared Parity Disk
Raid 4 does not support multiple
simultaneous write operations.
RAID 4 requires a minimum of 3
drives to be implemented. It is composed of independent disks with shared
parity to protect the data. Data transaction rate for
Read is exceptionally high and
highly aggregated. Similarly, the low ratio of parity
Disks to data disks indicates high
efficiency.
Disadvantages
Quite complex controller design
Worst Write transaction rate and
Write aggregate transfer rate
Difficult and inefficient data
rebuild in the event of disk failure
Block Read transfer rate equal to
that of a single disk
RAID Level 5: Independent Data Disk with distributed Parity Blocks
RAIDS 5 is Independent Distributed
parity block of data disks with a minimum
Requirement of at least 3 drives to
be implemented and N-1 array capacity. It helps in reducing the write inherence
found in RAID 4. RAID 5 array offers highest data transaction Read rate, medium
data transaction Write rate and good cumulative transfer rate.
Characteristics and
Advantages
Highest Read data transaction rate
Medium Write data transaction rate
Low ratio of ECC (Parity) disks to
data disks means high efficiency
Good aggregate transfer rate
Disadvantages
Disk failure has a medium impact on
throughput
Most complex controller design
Difficult to rebuild in the event
of a disk failure (as compared to RAID level 1)
Individual block data transfer rate
same as single disk
Recommended Applications
File and Application servers
Database servers
Web, E-mail, and News servers
Intranet servers
Most versatile RAID level
RAID Level 6:
RAIDS 6 are Independent Data Disk
array with Independent Distributed parity. It is known to be an extension of
RAID level 5 with extra fault tolerance and distributed parity scheme added.
RAID 6 is the best available RAID array for mission critical
Applications and data storage
needs, though the controller design is very complex
And overheads are extremely high.
Disadvantages
More complex controller design
Controller overhead to compute
parity addresses is extremely high
Write performance can be brought on
par with RAID Level 5 by using a custom
ASIC for computing Reed-Solomon
parity
Requires N+2 drives to implement
because of dual parity scheme
Recommended Applications
File and Application servers
Database servers
Web and E-mail servers
Intranet servers
Excellent fault-tolerance with the
lowest overhead
RAID Level 10:
RAID 10 is classified as the
futuristic RAID controller with extremely high Reliability and performance
embedded in a single RAID controller. The minimum
Requirement to form a RAID level 10
controller is 4 data disks. The implementation
Of RAID 10 is based on a striped
array of RAID 1 array segments, with almost the
Same fault tolerance level as RAID
1. RAID 10 controllers and arrays are suitable
For uncompromising availability and
extremely high throughput required systems
And environment. With all the
significant RAID levels discussed here briefly, another important point to add
is that whichever level of RAID is used regular and consistent data backup
maintenance using tape storage is must as the regular tape storage is best
media to recover from lost data scene.
Disadvantages
Very expensive / high overhead
All drives must move in parallel to
proper track lowering sustained performance
Very limited scalability at a very
high inherent cost
Recommended Applications
Database server requiring high
performance and fault tolerance
RAID Level 0+1:
It is the RAID array providing high
data transference performance with at least 4 disks needed to implement the
RAID 0+1 level. It's a unique combination of stripping
and mirroring with all the best
features of RAID 0 and RAID 1 included such as fast
data access and fault tolerance at
single drive level. The multiple stripe segments
have added high I/O rates to the
RAID performance and it is the best solution for maximum reliability.
Disadvantages
RAID 0+1 is NOT to be confused with
RAID 10. A single drive failure will cause the whole array to become, in
essence, a RAID Level 0 array
Very expensive / high overhead
All drives must move in parallel to
proper track lowering sustained performance
Very limited scalability at a very
high inherent cost
Recommended Applications
Imaging applications
General Fileserver
RAID LEVEL 50
RAID Level 50 requires a minimum of 6 drives to implement
Characteristics and Advantages
RAID 50 should have been called
"RAID 03" because it was implemented as a striped
(RAID level 0) array whose segments
were RAID 3 arrays (during mid-90s)
Most current RAID 50 implementation
is illustrated above
RAID 50 is more fault tolerant than
RAID 5 but has twice the parity overhead
High data transfer rates are
achieved thanks to its RAID 5 array segments
High I/O rates for small requests
are achieved thanks to its RAID 0 striping
Maybe a good solution for sites
that would have otherwise gone with RAID 5 but need some additional performance
boost
Disadvantages
Very expensive to implement
All disk spindles must be
synchronized, which limits the choice of drives
Failure of two drives in one of the
RAID 5 segments renders the whole array unusable.
