EC-Council: Computer Hacking Forensic Investigator(CHFI-V10) |
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Module 3 : Understanding Hard Disks and File Systems |
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RAID Storage System
Redundant Array of Independent Disks (RAID) is a technology that simultaneously uses multiple small disks, which function as a single large volume. RAID provides a method of accessing one or many separate hard disks, thereby decreasing the risk of losing all data if a hard disk fails or is prone to damage. Further, RAID helps in improving access time.
The RAID technology helps in the following:
▪ Maintain a large amount of data storage
▪ Achieve a high level of input/output performance
▪ Achieve great reliability through data redundancy
Levels of RAID Storage System
RAID 0- Disk Striping : Data
is split into blocks and written equally across multiple hard drives. It
improves I/O performance by spreading the I/O load across many channels and disk
drives. If any drive fails, data recovery is not possible. It does not provide
data redundancy. It requires a minimum of two drives for setting up.
RAID 1 -Disk Mirroring : RAID 1
generally executes mirroring as it duplicates, or copies drive data on two
different drives using a hardware RAID controller or software. If one of the
drives fails, the other functions as a single drive until the user replaces the
failed drive with a new one. The contents of the two disks are identical
RAID 2:It provides rapid access and increased storage by configuring two or
more disks as one large volume, similar to RAID 1. Data is written to a disk on
a bit level. Error correcting code (ECC) is used to verify whether the writes
are successful. It has better data-integrity checking but is slower than RAID 0.
RAID 3:It uses data striping and dedicated parity, and requires at least three
disks. Data is striped at a byte level across multiple drives, and one drive is
set to store parity information. If any drive fails, data recovery and error
correction is possible through the parity drive.
RAID 5:Data is striped at a byte level across multiple drives, and parity
information is distributed among all member drives. Data writing process is
slow. It requires a minimum of three drives for setup.
RAID 6 :RAID 6 (also known as double-parity RAID) is a type of RAID level in
which data is striped across various physical drives and it uses dual parity to
achieve better data redundancy than RAID 5. RAID 6 is similar to RAID 5 but
offers high fault and drive-failure tolerance. Its configuration requires
minimum of 4 drives, and the system stores an additional parity block on each
disk in the array to survive data losses in the event of double disk failure in
the array
RAID 10- Mirrored Striping :
It is a combination of RAID 0 (striping of volume data) and RAID 1 (disk
mirroring) and requires at least four drives to implement. It has same fault
tolerance as RAID level 1 and the same overheads as mirroring alone. It allows
mirroring of disks in pairs for redundancy and improved performance, and then
data is striped across multiple disks for maximum performance.
RAID 50 :It is a combination of RAID 5 (striping with parity) and RAID 0 (disk striping). Its configuration requires minimum of 6 drives. It provides a high degree of fault tolerance since one drive in each sub-array may fail without the loss of data.
RAID 60:Raid 60 is a combination of RAID 6 (distributed parity) and RAID 0 (disk striping). Its configuration requires minimum of 6 drives. It provides a high degree of fault tolerance since each of the RAID 60 sets can survive double disk failure without losing any data.
RAID 1E:It is a combination of RAID 1 (data mirroring) and RAID 0 (data striping). It requires minimum of 3 drives. RAID 1E extends RAID 1 data availability across an odd number of disks and hence avoids multiple disk failure.
RAID 5E:It is similar to RAID 5 but includes an integrated hot spare drive that can be used for input/output operations. It requires minimum of 4 drives.
RAID 5EE :It is similar to RAID level 5E and includes an additional hot spare drive for input/output operations. It requires minimum of 4 drives. In RAID 5EE, the spare area is distributed next to parity stripes.
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