An Overview of RAID - CompTIA A+ 220-801: 1.5

RAID (Redundant Array of Independent Disks)

• 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

RAID 0- Striping

• Five blocks are split between the physical drives
• High performance 
• Data written quickly
• No redundancy
• A drive failure breaks the array 

RAID 1- Mirroring

• File blocks are duplicated between physical drives
• High disk utilization
• Every file is duplicated
• Required disk space is doubled
• High redundancy
• Drive failure does not affect data availability 

RAID 5- Striping with parity

• File blocks are striped
• Along with a parity block
• Efficient use of disk space
• Files aren't duplicated but space is used for parity
• High  redundancy
• Data is available after drive failure
• Parity calculation may affect performance

RAID 1+0 - A stripe of mirrors 

•  The speed of striping, the redundancy of mirroring
• The best of both worlds
• Need at least 4 drives
• Can use more