Reference

RAID (0/1/5/10)

RAID combines multiple drives into one logical volume for speed, redundancy, or both. RAID 0 stripes data for speed with no protection; RAID 1 mirrors drives for safety; RAID 5 spreads data and parity to survive one drive failure; RAID 10 combines mirroring and striping.

Storage conceptsGeneral

RAID (0/1/5/10)

Also known as: RAID array, RAID 0, RAID 1, RAID 5, RAID 10

Combines drives for speed, redundancy, or both
RAID 0 = speed; RAID 1 = mirror; RAID 5/10 = both
Not a substitute for a real backup

The common RAID levels

RAID 0 stripes data across drives so reads and writes are faster and capacity adds up — but if any one drive fails, the whole array is lost. RAID 1 mirrors the same data onto two drives, so one can fail with no data loss, at the cost of using half the total capacity.

RAID 5 spreads data plus parity information across three or more drives, surviving any single drive failure while losing only one drive’s worth of capacity. RAID 10 mirrors and then stripes, giving both the speed of striping and the safety of mirroring, but needs at least four drives.

RAID is not a backup

Redundant RAID levels guard against a drive dying, which matters most for NAS units and servers that must stay online. But RAID protects only against hardware failure — it does not save you from accidental deletion, ransomware, theft, or fire, because those affect every drive at once.

For that reason RAID is best paired with a real backup kept on a separate device or offsite. Treat RAID as uptime insurance, not as your only copy.

Related terms

Keep reading the reference.

Cloud & backupNAS (network-attached storage)A NAS is a small storage appliance with its own drives that connects to your home or office network, so every device can read and write files to it over Wi-Fi or Ethernet. It acts like a private cloud you own — useful for backups, media, and offloading photos from a full phone.General Storage conceptsHDD (hard disk drive)An HDD (hard disk drive) stores data on spinning magnetic platters that a moving head reads and writes. It is slower than an SSD but much cheaper per gigabyte, which makes it a popular choice for large external drives and bulk archives.General Storage conceptsSSD (solid-state drive)An SSD (solid-state drive) stores data on flash memory chips with no moving parts, so it reads and writes far faster than a spinning hard drive. SSDs are the standard internal storage in phones, tablets, and modern laptops, prized for speed, silence, and shock resistance.General Cloud & backupDifferential backupA differential backup saves everything that changed since the last full backup. Each differential grows over time because it always references the full backup, but restoring is simple: you only need the full backup plus the most recent differential.General