Create and Manage Raid Devices
What is RAID?
RAID stands for Redundant array of independent disks. With raid we can combine multiple storage devices into one combined storage area.
Level 0 array (striping): Suppose we have multiple storage devices and we want to combine them, now RAID will create a Level 0 storage area which is visible to linux and is known as stripe. Issue with this is if one storage device is lost we lose the whole array (array is the storage space comprised of those multiple storage devices which are now combined). Now stripe area is actually redundant which means if one disk fails we can recover from other disks while its not the same with Level 1 array which is known as mirrored array.
Level 1 array (mirroring): In this array all the data is duplicated in all the disks which means if one is lost we still have multiple exact copies of data which we can recover from other disk devices. This makes this array redundant.
Level 5 array: A minimum of 3 disks is required to create this array. In Level 5 array if one disk fails we can still recover data from other disk and use parity to rebuild rest of the data, parity is stored on each disk to help build lost data. Parity is like some extra information or a small backup which can be used to rebuild lost information so if we lose one disk we'll still have some parity on other disks. This is permanent that exactly one disk can be lost and data should still be recoverable.
Level 6 array: In Level 6 array all things are similar to Level 5 array except we need minimum of 4 devices and 2 disk exactly can be lost and data should still be recoverable.
Level 1+0 array or Level 10 array: Level 10 array is a combination of Level 0 and Level 1
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