What does SMART mean, and how do you read it?

SMART is the self-monitoring data that drives keep about their own health: warnings, errors, wear and running hours. Pulse by Zaweba reads it and shows the parts that matter in plain terms. For NVMe drives that means the critical warning flags, the available spare and its threshold, the percentage of rated life used, media errors, power-on hours and temperature, all without administrator rights.

The name stands for Self-Monitoring, Analysis and Reporting Technology. It has been built into hard drives and SSDs for many years, but Windows doesn't put it in front of you, so most people never look at it until something goes wrong.

The figures that matter on an NVMe drive

Open the Temperatures page in Pulse (Ctrl+2) and find the Drive health group. Each drive has its own entry.

Critical warning flags are the drive's own way of saying something is wrong. Normally none are set. If one appears, take it seriously and make sure your files are backed up.

Available spare is the pool of reserve space the drive uses to replace worn-out areas. It starts at or near 100 per cent. The threshold beside it is the level the maker considers the minimum; falling below it means the drive is running out of room to heal itself.

Percentage of rated life used is how much of the drive's designed write endurance has been used up. It climbs slowly over the years. It can go past 100, because the rating is a guarantee, not a cliff edge, but a high figure is a good reason to plan a replacement.

Media errors count the times the drive could not read or write data correctly. On a healthy drive this is zero, and a rising count is a bad sign.

Power-on hours is simply how long the drive has been running in total. It doesn't measure health by itself but helps you judge the age of a drive, especially a second-hand one.

Older SATA drives and USB cases

Older SATA drives and drives in USB cases report SMART differently, and Windows only lets administrators read them. Pulse reads these through its optional sensor helper. Turn on Settings > Sensor readings, Windows asks for permission, and a small helper starts that only reads sensors, accepts no commands and stops when Pulse closes. Hard drives also report reallocated sectors, the count of damaged areas the drive has swapped out for spares; a growing figure there means the surface is wearing.

Reading it sensibly

One reading is a snapshot. What you want to know is the trend. A drive with 20 per cent of its life used after five years is in good shape; one that has jumped ten points in a month is being worked very hard. A single media error is worth noting. Several new ones in a week are worth acting on.

You don't have to keep checking, because Pulse watches for you. The drive health alert is on by default. It fires when a drive reports a critical warning, new media errors or reallocated sectors, spare capacity below its threshold, or 90 per cent of rated life used. The notice appears once as a Windows notification and is kept in the alert log.

What to do with bad news

SMART can't repair a drive, and it can't promise one won't fail without warning. What it gives you is time. If Pulse by Zaweba reports a decline, copy anything important somewhere else first, then look at replacing the drive. A good backup routine is the real protection; SMART simply tells you when to stop putting it off.