Set 2 — RAID Levels and Fault Tolerance

RAID

Combines multiple physical disks into one logical disk in the OS

RAID 0

Striping only - fast, NO redundancy, min 2 disks, full capacity used

RAID 1

Mirroring - full redundancy, min 2 disks, only 50% usable capacity

RAID 5

Striping + single parity - min 3 disks, survives 1 drive failure

RAID 6

Striping + dual parity - min 4 disks, survives 2 drive failures

RAID 10

Mirroring + striping combined - min 4 disks, fast AND redundant

Striping

Splits data evenly across multiple drives at the same time (speed boost)

Mirroring

Writes identical copies of data to two or more drives (redundancy)

Parity

Extra calculated data stored so a lost drive's data can be rebuilt

Most common RAID in business/servers

RAID 5

Failure Resistant

Protects against data loss if a single disk fails (RAID 1 or 5)

Fault Tolerant

System keeps RUNNING even if a component fails (RAID 1 or 5)

Disaster Tolerant

Two independent zones with full access to data at all times (RAID 10)

Hot spare

An extra idle drive that automatically takes over when one fails

Minimum disks - RAID 0

2

Minimum disks - RAID 1

2

Minimum disks - RAID 5

3

Minimum disks - RAID 6

4

Minimum disks - RAID 10

4