How Storage Works
A seed for a note about where our data actually sits: from punched tape and the first hard disk to SSDs and NVMe, file systems, RAID – and why a NAS is called a NAS.
Open in the interactive Digital Garden
The name of this site comes from a Network-Attached Storage, so a note about storage was overdue. In From Source Code to Silicon I followed a program down to the transistors; this note will follow a file down to the magnetic spot or the electrons in a flash cell.
What I Want to Cover
- History: punched cards and tape, IBM's first hard disk in 1956 (the size of two big fridges, for about 5 million characters), floppies, CDs, and the arrival of flash.
- How a hard disk works: spinning platters, a head flying a few nanometres above them, and why a dropped laptop with an HDD is bad news.
- How an SSD works: flash cells, why they wear out, what TRIM does, and what "TBW" on the box means.
- File systems: NTFS, ext4, Btrfs, ZFS – what a file system does and what snapshots and checksums add.
- RAID: mirrors and parity – and once more, why RAID is not a backup (see Constructing a Backup).
- Example: reading the SMART health data of my disks and what the numbers mean.
Tools for checking disks are in my Backup & Recovery resources.