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What is RaID ?

What is RaID ?. Christopher J Dutra Seton Hall University. 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.

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What is RaID ?

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  1. What is RaID? Christopher J Dutra Seton Hall University

  2. 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.

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

  4. 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.

  6. RAID Limitations • RAID won’t protect data loss against: • viruses • power surges • multiple hardware failures (sometimes) • sabotage • IMPORTANT : MAINTAIN CURRENT BACKUPS.

  7. 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.

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

  9. 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.

  10. RAID 5 • RAID level 5—one 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)

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

  12. 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 PC’s –do not necessarily need RAID, could help in the future though (as video games and other applications become more costly in resources).

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