Hardware Reliability: Storage & Power

How an SD card tells you it's dying

Consumer SD cards in a streaming device typically last 6-18 months. Failure escalates in stages:

1. Intermittent slowness. The dashboard takes longer to load, boots get slower. The card's controller is remapping failing cells.
2. Random write failures. Settings don't persist across reboots, logs show I/O errors, the filesystem occasionally remounts read-only.
3. Boot failure. Solid red LED with no green ACT activity on power-up: the boot files landed on a dead cell. Re-flashing the same card may work once by landing on healthier cells, but the card is untrustworthy from here on.

Storage choice

Endurance is rated in TBW, the terabytes written before the card is expected to fail. The classes differ by an order of magnitude:

• Bigger cards last longer. A 64 GB card has more wear-leveling headroom than a 16 GB one, but endurance class trumps capacity class.
• Recording multiplies wear. 1080p H.264 at 4 Mbps writes roughly 30 MB per minute, or about 1.8 GB per hour of recording. If you record on the device, buy industrial or record to a USB stick instead of the boot card.

Power: the failure that impersonates SD wear

Undervoltage is the second-biggest cause of SD corruption after wear. A brownout to 4.5 V makes SD writes fail mid-stripe in a way that looks identical to a worn-out card. If cards keep "dying" on one airframe, suspect the power rail before the card.

• On the bench: use the official Raspberry Pi PSU, 5 V / 3 A for the Pi 4. Phone chargers work most of the time and fail at exactly the wrong moment.
• On the airframe: use a dedicated 5 V / 3 A+ BEC for the Pi, not a hobby BEC tapped off the same rail as the ESCs. ESC switching noise on a shared rail causes brownouts that are indistinguishable from a bad PSU.
• Wiring matters: undersized power leads drop voltage under load. Short, thick wires from the BEC to the Pi's 5 V input.

To check whether the Pi has seen undervoltage since boot, run this over SSH:

vcgencmd get_throttled

throttled=0x0 is healthy. Any other value means undervoltage or thermal throttling occurred, so fix the power or cooling before the next flight.

Power-loss practice

Yanking power mid-write is the top cause of boot-partition corruption. The operational rules:

• Shut down cleanly when you can: sudo shutdown -h now over SSH, wait for the green ACT LED to stop blinking entirely, then remove power.
• When you can't control the power sequence (battery swaps, field ops), a small UPS HAT (~$25) detects supply loss and gives the Pi ~10 seconds on its own cell to shut down cleanly.