RAID Comptia A+ 220-1101

data redundancy

• Hard drives store huge amounts of important data

• Hard drives are moving components

- They will eventually break

• What happens to the data when the drive fails? - You can prepare for that; Use an array of drives

• RAID is not backup

RAID

Redundant Array of Independent Disks

- They're also inexpensive disks

Different RAID levels

- Some redundant, some not

RAID 0 - Striping

RAID 1- Mirroring

RAID 5 - Striping with parity

Nested RAID - RAID 1+0 (a.k.a. RAID 10)

- A stripe of mirrors

Software RAID vs Hardware RAID

*Software-based RAID

• A feature of the operating system

• Doesn't require any special hardware

• Usually lower-performance than hardware-based

*Hardware-based RAID

• A feature of the hard drive controller

• Configured outside of the OS

• Usually invisible to the operating system

• High performance, designed for speeds

Hot swappable drives

• Add and remove while the system is running

• The connection is "hot"

• Drive chassis

• Two or more drives

• Easy to repair

• Replace a drive while the system is running

• Combine with RAID for 100% uptime

RAID 0 (striping)

• File blocks are split between physical drives

• High performance

• No redundancy

• Minimum of 2 drives

RAID 1 (mirroring)

• File blocks are duplicated

between physical drives

• High disk space utilization

• High redundancy

• Minimum of 2 drives

RAID 5 - Striping with Parity

• File blocks are striped along with a parity block

• Efficient use of disk space

• High redundancy

• Minimum of 3 drives

RAID 10 (1+0) - A stripe of mirrors

• The speed of striping, the redundancy of mirroring

• The best of both worlds

• Need at least 4 drives