Definition
RAID 5 stripes data and distributed parity across at least three disks, allowing the array to tolerate one disk failure.
How it works
With n equally sized drives, usable capacity is approximately n minus one drives. Small writes can require multiple reads and writes to update parity. After a drive fails, missing blocks are reconstructed from the surviving members.
Real-world example
Three 2 TB drives in RAID 5 provide roughly 4 TB usable before formatting overhead. During reconstruction after replacing a failed disk, a second disk failure can result in array loss.
Limits and best practices
Consider drive capacity and rebuild duration carefully. RAID 5 may be a poor fit for very large disks or write-heavy workloads; evaluate RAID 6 or RAID 10 based on workload and risk, and keep independent backups.
Technical detail to remember
RAID 5 reconstruction heavily reads surviving members; an additional unreadable disk during recovery can make data unavailable. Evaluate rebuild duration, read errors and drive sizes before selecting this RAID level.