RAID Levels, continued

• RAID-5: three or more disks of the same size are combined through striping, parity data is scattered over all disks
• Disks should be of the same size
• Array will recover if one disk is lost, but not two or more
• Minimal storage overhead (smaller for large arrays)
• Good read performance (but not as good as RAID-4, because reads must skip over parity data)
• Write performance is better than for RAID-4, similar to RAID-1

Hey, but wait, where are...

• RAID-2: similar to RAID-4 but stores error-correcting codes (ECC) instead of parity
• Not supported by Linux Software RAID
• Rarely used, made obsolete by modern disks
• RAID-3: similar to RAID-4 but stripes data at byte level
• Byte-level striping requires hardware support, including spindle synchronization
• Not supported by Linux Software RAID
• Rarely used, made impossible by modern disks