Choosing the right RAID level is one of the most critical decisions a server administrator will make. RAID, or Redundant Array of Independent Disks, provides varying degrees of performance, redundancy, and capacity depending on the level selected. Understanding the trade-offs between RAID 0, 1, 5, 6, and 10 is essential for matching your storage configuration to workload requirements.
Comparing RAID 5 and RAID 10
RAID 5 stripes data across three or more disks with distributed parity, offering a good balance between usable capacity and fault tolerance. However, rebuild times on large drives can be painfully slow, leaving the array vulnerable during reconstruction. RAID 10, which mirrors pairs of striped disks, delivers superior write performance and faster rebuilds at the cost of 50% usable capacity.
For database servers handling heavy random I/O, RAID 10 is almost always the better choice. Web servers and file servers with predominantly sequential reads may benefit from RAID 5's higher usable capacity. Always factor in the time-to-rebuild metric when planning for drives larger than 500 GB, as the probability of a second drive failure during rebuild increases with drive size.
Modern hardware RAID controllers from vendors like LSI and Adaptec include battery-backed write caches that dramatically improve write performance. Ensure your controller's battery is regularly tested and replaced, as a failed BBU forces the controller into write-through mode, which can degrade performance by 80% or more.