What is hard drive/SSD firmware?
Firmware is the storage device’s operating system. Just like you may run a Windows operating system on your computer and run an IOS or Android operating system for your phone, a complicated device needing to store and organize billions of bits onto platters or NAND needs an operating system. I personally prefer the term hard drive operating system or HDD O/S instead of firmware. Either is accurate, but the term firmware tends to have a connotation that it’s nothing special or unique. One would expect the firmware for multiple electronic devices coming off a manufacturing line to be identical, but this is not the case in the world of storage.
The firmware on a spinning disk will have all the compiled application code for doing everything the drive needs to do. This baseline firmware will vary slightly from O/S revision to O/S revision. Hard drive manufacturers are always making tweaks to this code for increased performance, security and reliability. Some manufacturers will produce hundreds of versions of their base firmware in a calendar year. For any particular drive-line, like the Western Digital Blue desktop series, they may have ten or twenty revisions a year.
HDD manufacturers will sometimes create custom firmware for different computer companies; Apple likes to have their own firmware as one example. They will code different drive behavior for drives intended for enterprise data centers, consumer desktops, consumer DVR units, etc. A consumer drive like a WD Green will spin down its platters and park the heads during inactivity, as opposed to a WD Enterprise drive that will keeping spinning until a RAID controller tells it to spin down. These behaviors are defined in the firmware.
The firmware zone is also where a lot of the drive’s unique calibrations, defect lists, zone tables, unique translation (addressing) information, performance logs and SMART attributes are stored.