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BSD Today: Configuring RAID on NetBSD

Aug 24, 2000, 01:57 (2 Talkback[s])
(Other stories by Peter Clark)

[ Thanks for this link to Jeremy C. Reed, who notes that this is "...Not necessarily a Linux article -- but it has some great descriptions of RAID terminology and usage." ]

"RAID is an acronym for "Redundant Array of Inexpensive Disks". The purpose of RAID is both to join more than one disk into a single logical device and to prevent a single physical disk failure from causing the entire logical device to fail."

"RAID 0 is also known as striping. It simply consists of joining two or more disks into a larger logical device. It does not provide any redundancy in itself, but is commonly used to combine RAID sets utilizing other RAID levels, such as RAID 1 or RAID 5. A striped RAID 1 set is known as RAID 0+1 or RAID 10. Likewise, a striped RAID 5 is known as RAID 0+5 or RAID 50. RAID 1 is also known as mirroring. Two disks are combined -- each contain the same data. If one disk fails, the other continues on and the logical device remains available."

"RAID 4 combines three or more disks into a single device with one of the disks dedicated to parity. If one disk fails, the logical device will remain available, but with degraded performance. This RAID level is not commonly used because the single parity disk introduces a considerable bottleneck for writes. RAID 5 combines three or more disks into a single device with the parity distributed across each drive in the set. If one disk fails, the logical device will remain available, but with degraded performance."

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