What is RaID?

1
What is RaID?

• Christopher J Dutra
• Seton Hall University

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What is RAID?

• RAID stands for a redundant array of inexpensive
  disks. (sometimes inexpensive is replaced with
  independent).
• RAID is a storage scheme in which many hard disks
  are bundled together in an array to act as one
  disk.
• Developed by UC-Berkley scientists in 1987.

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Benefits

• Higher Data Security
• Fault Tolerance
• Improved Availability
• Increased Storage Capacity with Integrated Disks
• Improved Performance

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Higher Data Security

• A RAID can still operate if a single disk inside
  the RAID fails.
• Also would not require any data to be restored
  from a backup disk.
• Primary reason why people purchase RAIDs.

5
Tradeoffs

• There are three components to RAID servers to
  consider when purchasing
• Speed overall performance, capacity
• Reliability amount of fault tolerance expected
• Cost amount you are willing to spend.
• General rule of thumb is pick two.
• Also, for complex raid servers, hours of setup
  and maintenance is expected.

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RAID Limitations

• RAID wont protect data loss against
• viruses
• power surges
• multiple hardware failures (sometimes)
• sabotage
• IMPORTANT MAINTAIN CURRENT BACKUPS.

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RAID LEVELS

• RAID 0 Files are broken into stripes of a
  user-defined size of the array, and stripes are
  sent to each disk in the array.
• It has worse reliability than a hard disk, used
  for greater performance. Cheap to implement, but
  not very reliable. Must maintain current backups
  should RAID 0 fail.

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Example of RAID 0
This is a four-disk, 16 KB
stripe size RAID 0 array.
Source www.pcguide.com
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RAID 1

• RAID 1 has its data duplicated on another hard
  disk. That way, should one of the hard drives
  fail, the other is operable until the faulty
  drive is replaced.
• Also, a technique called duplexing provides fault
  tolerance against either hard drive or the RAID
  controller.
• Performance is compromised slightly.

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RAID 5

• RAID level 5one of the most popular RAID
  configurations, RAID 5 stripes both data and
  parity information across three or more drives.
• Fault tolerance is maintained by ensuring that
  the parity information for any given block of
  data is placed on a drive separate from those
  used to store the data itself. (pcguide.com)

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Example of RAID 5
This is a four-disk, 16 KB stripe size RAID 5
array.
Source www.pcguide.com
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Why buy RAID?

• Business servers provides data protection
  (especially good for when loss of data could
  cripple a business)
• Workstations for graphical design, video
  editing, a RAID system would improve the
  performance of high-overhead programs (such as
  3dStudio Max).
• Regular PCs do not necessarily need RAID, could
  help in the future though (as video games and
  other applications become more costly in
  resources).