# RAID Drive Anatomy By Numa Topic: Computing, AI & Electronics [Open the interactive Jig](https://ask.jig.com/j/WKAJJPlwVuXc) ## Guide ### 1. RAID Drive Anatomy Your photos, games and messages live on drives like these four\. Teaming several drives together is called RAID, short for Redundant Array of Independent Disks\. A team can be faster, safer, or both\. Let's open them up\. ### 2. Inside a hard drive Under each lid, shiny discs called platters spin on a motor\. Data is stored as millions of tiny magnetic spots arranged in rings called tracks\. Most drives spin 5,400 to 7,200 times a minute: up to 120 turns every second\. Here they are slowed down so you can watch\. ### 3. The arm that reads An arm called the actuator swings a tiny head across the platter to find the right track\. A coil of wire between magnets pushes the arm, the same trick a loudspeaker uses\. The head floats on a cushion of air and never touches the disc\. A drive with two platters has four heads, one for each side of each platter\. ### 4. RAID 0: split it up RAID 0 cuts a file into pieces called blocks and spreads them across all the drives, a row at a time\. That row is called a stripe\. All four drives work at once, so it's fast and you get all the space\. Stop a drive and see what happens\. RAID 0 has no spare copy: if one drive fails, every file is missing pieces\. ### 5. RAID 1: keep a twin RAID 1 writes exactly the same blocks to two drives, like keeping an identical twin of every file\. If one drive stops, its twin still holds everything\. The cost: two drives give you the space of one\. ### 6. RAID 5: a clever safety net RAID 5 stripes data across the drives and adds one parity block to every row, shown here with stripes\. Parity is a small sum of the other blocks in its row, so it can recreate any one missing block\. It moves from drive to drive, so no single drive does all the extra work\. Think of a sum: if 4 \+ 3 \+ 5 = 12 and the 3 goes missing, 12 minus 4 minus 5 brings it back\. ### 7. Losing a drive, then rebuilding In RAID 5 one drive can fail and every file stays readable\. Swap in a new drive and the controller, the array's own little computer, rebuilds each missing block, row by row, from the blocks that are left\. Rebuilding a big drive can take many hours\. Until it finishes, a second failure would lose data\. ### 8. RAID is not a backup RAID keeps working when a drive breaks, but it copies mistakes too: delete a file and it vanishes from every drive\. Fire or a flood can take the whole box\. So keep a separate backup as well\. Other levels mix the ideas: RAID 6 survives two failed drives, and RAID 10 mirrors pairs of drives, then stripes across them\.