ITC 3306
RAID Levels
Columbia Southern University ITC
3306: Operating Systems
RAID Levels
What is RAID?
RAID stands for Redundant Array of Independent Disks which is a storage technology
that creates a data loss fail-safe by merging two or more hard disk drives into one interconnected
storage unit. According to authors McHoes & Flynn (2018), RAID technology was proposed by
researchers at the University of California to emphasize the scheme’s improved disk performance
and reliability (p.237). RAID is based on the idea that several small-capacity disk drives are
superior to few large-capacity disk drives because the device can access the requested data from
several drives simultaneously by spreading the data through several smaller disks (McHoes &
Flynn, 2018). Due to design and architecture of RAID, in case if there is disk failure, the
recovery of data is guaranteed by redundant disk capacity (Garg & Verma, 2017). RAID consists
of seven levels, level 0 through 6 but four commonly used are 0, 1, 5 and 6 (Garg & Verma,
2017).
RAID 0
This level distributes the data evenly over all available drives, resulting in very high read
and write performance but offering no additional redundancy at the same time. RAID level 0 is
not considered as a true member of RAID family because it is the only level that uses data
striping without parity and doesn’t provide error correction (McHoes & Flynn, 2018). The
purpose is to speed up performance as organizing data in such a way where it allows faster
reading and writing of files (Daniel, 2020).
, The benefit of RAID level 0 is data is stripped into multiple drives and disk space is fully
utilized. The diagram shows how data is distributed into blocks on two disks, example block 1
and block 2 as second one. As shown in diagram below, when the OS issues a read command for
first strips, data can be transferred in parallel and that’s how it improves system performance. It
increases speed and space both so you can back up more files faster. Since the request can be
handled in parallel for number of strips, it reduces the transfer time (Garg & Verma, 2017).
Block 1 Block 2
Block 3 Block 4
Block 5 Block 6
Block 7 Block 8
Disk 1 Disk 2
RAID 1
RAID level 1 uses data striping just like RAID level 0 but the difference between two is
in RAID 1, each logical strip is mapped to two distinct physical disks. Basically, it mirrors the
disk that contains the same data, meaning every disk in the array has a copy disk containing same
information (Garg & Verma, 2017). Author Taneja has mentioned in his article, “RAID 1, also
known as mirroring, is essentially where you have two disk drives and whatever you put on disk
one, you simultaneously put on disk two. The idea is that if one of those two disks dies, then you
have the other disk that is still working and therefore you achieve data availability
improvements” (Taneja, 2009). The information is replicated from one drive to another every
time you insert information.
One of the biggest advantages of using RAID 1, is it is the safest option for your data. If
in case one drive is lost, the same exact data still exists in the other drive and takes no time to
RAID Levels
Columbia Southern University ITC
3306: Operating Systems
RAID Levels
What is RAID?
RAID stands for Redundant Array of Independent Disks which is a storage technology
that creates a data loss fail-safe by merging two or more hard disk drives into one interconnected
storage unit. According to authors McHoes & Flynn (2018), RAID technology was proposed by
researchers at the University of California to emphasize the scheme’s improved disk performance
and reliability (p.237). RAID is based on the idea that several small-capacity disk drives are
superior to few large-capacity disk drives because the device can access the requested data from
several drives simultaneously by spreading the data through several smaller disks (McHoes &
Flynn, 2018). Due to design and architecture of RAID, in case if there is disk failure, the
recovery of data is guaranteed by redundant disk capacity (Garg & Verma, 2017). RAID consists
of seven levels, level 0 through 6 but four commonly used are 0, 1, 5 and 6 (Garg & Verma,
2017).
RAID 0
This level distributes the data evenly over all available drives, resulting in very high read
and write performance but offering no additional redundancy at the same time. RAID level 0 is
not considered as a true member of RAID family because it is the only level that uses data
striping without parity and doesn’t provide error correction (McHoes & Flynn, 2018). The
purpose is to speed up performance as organizing data in such a way where it allows faster
reading and writing of files (Daniel, 2020).
, The benefit of RAID level 0 is data is stripped into multiple drives and disk space is fully
utilized. The diagram shows how data is distributed into blocks on two disks, example block 1
and block 2 as second one. As shown in diagram below, when the OS issues a read command for
first strips, data can be transferred in parallel and that’s how it improves system performance. It
increases speed and space both so you can back up more files faster. Since the request can be
handled in parallel for number of strips, it reduces the transfer time (Garg & Verma, 2017).
Block 1 Block 2
Block 3 Block 4
Block 5 Block 6
Block 7 Block 8
Disk 1 Disk 2
RAID 1
RAID level 1 uses data striping just like RAID level 0 but the difference between two is
in RAID 1, each logical strip is mapped to two distinct physical disks. Basically, it mirrors the
disk that contains the same data, meaning every disk in the array has a copy disk containing same
information (Garg & Verma, 2017). Author Taneja has mentioned in his article, “RAID 1, also
known as mirroring, is essentially where you have two disk drives and whatever you put on disk
one, you simultaneously put on disk two. The idea is that if one of those two disks dies, then you
have the other disk that is still working and therefore you achieve data availability
improvements” (Taneja, 2009). The information is replicated from one drive to another every
time you insert information.
One of the biggest advantages of using RAID 1, is it is the safest option for your data. If
in case one drive is lost, the same exact data still exists in the other drive and takes no time to
