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RAID Arrays. A short summary for TAFE. What is a RAID. A Raid Array is a way of protecting data on a hard drive by using “redundancy” to repeat data across a number of drives. If one drive fails, the data can be retrieved (in most cases). Types of RAID arrays.
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RAID Arrays A short summary for TAFE
What is a RAID • A Raid Array is a way of protecting data on a hard drive by using “redundancy” to repeat data across a number of drives. • If one drive fails, the data can be retrieved (in most cases)
Types of RAID arrays • JBOD (Just a bunch of Disks). Technically not a RAID array, as there is no redundancy, a group of smaller disks joined together to make one big volume.
RAID 0 • Again, not technically a RAID Array. • No redundancy, but allows for data to be “striped” across two or more disks. (Very fast transfer) • Loss of one disk is fatal to the system
RAID 1 • Data is duplicated across two disks. Loss of one disk is not fatal, but there is huge redundancy. Two 300GB HDDs in a RAID 1 array will give a 300GB volume, so you’ve halved your space…
RAID 3 • Several disks with data striped plus a parity disk (using block level parity and hamming codes) • Usually the parity disk is the first to fail, so not used.
RAID 4 • An improvement on RAID 3, but not used much, for the same reason: parity disk is usually the first to fail.
RAID 5 • This is the commonly used array type. • Three or more disks with striping and block level parity shared across all disks. • Four 300GB disks show one 900GB volume (1-n drives)…