How The RAID Calculator Works
The calculator uses the standard RAID capacity formulas for each level: RAID 0 gives n × D (all drives, zero redundancy); RAID 1 gives D (all drives mirror the same data); RAID 5 gives (n-1) × D (one drive's worth lost to parity); RAID 6 gives (n-2) × D (two drives lost to dual parity); RAID 10 gives (n/2) × D (mirrored pairs then striped). Nested levels like RAID 50 and 60 divide drives into groups, apply RAID 5 or 6 within each group, then stripe across groups. The calculator validates minimum drive counts (3 for RAID 5, 4 for RAID 6, even for RAID 10) and flags invalid configurations instead of silently producing nonsense numbers.
Choosing A RAID Level In 2026
For home and prosumer builds, the conventional wisdom has shifted toward RAID 6 (or its ZFS equivalent, RAIDZ2) for any array built from drives 8 TB or larger. The reason is rebuild time: when a drive fails in a RAID 5 array, the controller has to read every sector on every surviving drive to reconstruct the lost data. On modern high-capacity drives, that rebuild can take 24-48 hours, during which a second drive failure would mean total data loss. With RAID 6's two parity drives, you can survive a second failure mid-rebuild. For sub-8 TB drives and arrays of 4-5 drives total, RAID 5 is still fine; the rebuild window is shorter and the overhead of a second parity drive isn't worth it.
RAID 10 vs RAID 5/6 For Performance
The calculator's speed multipliers tell the story: RAID 10 has a write multiplier equal to n/2 (full speed on each mirror pair, striped across pairs), while RAID 5 has roughly (n-1) × 0.75 and RAID 6 roughly (n-2) × 0.5. The reason is the write penalty on parity RAIDs: a small write requires reading the old data block, reading the old parity, computing new parity, and writing both blocks back — four I/Os for one logical write. For database workloads and VM hosts where random small writes dominate, RAID 10 crushes RAID 5/6 despite using more raw capacity. For sequential workloads (media libraries, backups) the gap closes and parity RAIDs are competitive.
RAID Is Not A Backup Strategy
The single most-repeated piece of storage advice holds: RAID protects against drive failure, not data loss. A ransomware attack encrypts every drive in your array simultaneously; a fire or flood takes them all out; a careless "rm -rf" wipes data from every mirror at once. The 3-2-1 rule still applies on top of any RAID: three copies of important data, on two different media, with at least one off-site. For home setups, a weekly rsync or BackBlaze Personal Backup covers the off-site leg cheaply. For business, cloud backup services (Backblaze B2, AWS S3 Glacier) make the off-site copy essentially free at small scale. Your RAID gets you through a dead disk; your backup gets you through everything else.
