RAID technology allows you to combine multiple physical hard drives in to a single virtual disk. This virtual disk can provide improved performance through striping and protect against data loss through mirroring or parity.
Striping splits your data across multiple drives. Simultaneously reading or writing to multiple drives improves performance, but without redundancy, if a single disk fails, all data is lost.
Mirroring writes the same data to a second drive, this provides redundancy. If one drive fails the data remains available on the other. Write speed is not improved because the same data must be written to both drives.
Read speed is improved as when reading the drives can operate in the same way as a striped set. Parity provides redundancy by storing information that allows the contents of a failed disk to be rebuilt.
A scheme using both striping and parity also improve performance. Different RAID schemes, also known as levels, use these tools in different ways. Each RAID level offers a different balance between performance, redundancy and capacity.
We'll look more closely at the different RAID levels in another video. Remember that RAID is not a substitute for backups. Data stored in a RAID array is still vulnerable to accidental deletion or modification.
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