RAID
Hardware & InfrastructureRAID is a storage technology that combines multiple physical drives into one logical unit to improve performance, increase fault tolerance, or both. Depending on the RAID level, data is striped, mirrored, or protected with parity so a server can keep running after a drive failure. RAID is common in hosting servers, but it is not a substitute for backups.
How It Works
RAID (Redundant Array of Independent Disks) is implemented by a hardware RAID controller or software RAID in the operating system. It presents several disks as a single volume, then distributes data across them according to a chosen RAID level. The main techniques are striping (splitting data across drives for speed), mirroring (duplicating data for redundancy), and parity (storing calculated recovery information).
Common RAID levels include RAID 0 (striping only, no redundancy), RAID 1 (mirroring), RAID 5 (striping with single-parity, tolerates one drive failure), RAID 6 (double-parity, tolerates two drive failures), and RAID 10 (mirrored pairs striped together). Rebuilds occur after a failed drive is replaced, but rebuild time and performance impact depend on drive size, workload, and whether the array uses HDDs or SSDs. RAID improves availability, yet it cannot protect against accidental deletion, corruption, malware, or a full server loss, so separate backups remain essential.
Why It Matters for Web Hosting
RAID affects uptime, performance consistency, and risk when hardware fails. When comparing hosting plans, look for what RAID level is used, whether storage is SSD or HDD, and how failures are handled (hot spares, monitoring, and replacement process). RAID 10 often favors performance and fast recovery for databases, while parity-based RAID can be more capacity-efficient. Regardless of RAID, confirm the provider offers independent backups and a clear restore process.
Types of RAID
- RAID 0: maximum performance and capacity, but any drive failure loses the array
- RAID 1: simple redundancy via mirroring, good read performance, uses 50% capacity
- RAID 5: single-parity protection, capacity-efficient, slower writes and rebuild sensitivity
- RAID 6: double-parity protection, better fault tolerance than RAID 5, higher write overhead
- RAID 10: combines mirroring and striping, strong performance and resilience, higher capacity cost
RAID vs Backups
RAID is designed for availability during drive failures, while backups are designed for recovery from data loss events. RAID can keep a site online if a disk dies, but it will faithfully mirror or parity-protect deleted files, corrupted databases, or encrypted data from ransomware. Backups stored separately (ideally off-server and versioned) let you roll back to a known-good point in time, which RAID alone cannot provide.