7 SSD health numbers you should be checking every month

Published Oct 30, 2026, 2:30 PM EDT Monica J. White is a journalist with over a decade of experience in covering technology. She built her first PC nearly 20 years ago, and she has since built and tested dozens of PCs. PC hardware is her main beat, and graphics cards and the GPU market at large are her main area of interest, but she has written thousands of articles covering everything related to PCs, laptops, handhelds, and peripherals. From GPUs and CPUs to headsets and software, Monica's always willing to geek out over all things related to computing. Outside of her work with How-To Geek, Monica contributes to TechRadar, PC Gamer, Tom's Guide, Laptop Mag, SlashGear, Whop, and Digital Trends, among others. Her ultimate goal is to make PC gaming and computing approachable and fun to any audience. Monica spends a lot of time elbow-deep in her PC case, as she's always making upgrades, testing something, or plotting out her next build. She's the go-to tech support person in her immediate circle, so she's never out of things to do. Whenever she has spare time, you'll find her gaming until the early hours and hanging out with her dog. Did you know that your SSD can fail even at 100% health? Cheerful, isn't it? HDDs are unpredictable too; a study shows that half of the ones that fail do so within their first year. Amazing. This might make it sound like the odds are not at all in our favor here, but I prefer to play it safe with my hardware, which is why I always check my SSDs' SMART health data. Here are the parameters I check once a month at minimum. You can check them yourself with CrystalDiskInfo or another similar program. Unsafe shutdowns Unexpected power losses can leave traces in your SSD's health data I just had a black screen, also known as a blue screen of death, earlier today. What gives? I'm not sure what my PC's problem was, but Windows can probably be to blame. In any case, when your PC shuts down without warning, that's called an unsafe shutdown, and your SSD doesn't love that. Your NVMe SSD actually keeps track of these (and undoubtedly holds quite the grudge) through a SMART attribute called Unsafe Shutdowns. The counter increases whenever the drive loses power without receiving a proper shutdown notification. That can happen during power outages, forced shutdowns, or unexpected crashes. This isn't great because any data that was still being written could potentially be lost or corrupted. (Fun fact, data corruption can sometimes be caused by RAM, not the SSD.) A few unsafe shutdowns shouldn't kill your SSD, but if they keep happening, you should investigate what's going on. Don't be me and just ignore it like I did literally two hours before sitting down to write this article ... Temperature Some like it hot. SSDs don't SSDs can run surprisingly hot, and while a heatsink can help, it can't fully prevent those temps from ramping up on occasion. Your SSD getting too hot isn't always a problem, but it can start throttling its performance to protect itself. This is good in the long run, as slow but safe data is better than fast and compromised, but it's not ideal. Many consumer SSDs have an operating temperature range that tops out at around 70 degrees Celsius, although the exact limits vary between models. Total host writes This tells you how much data you've actually written to your SSD Every SSD has a finite write endurance, usually expressed as TBW, or terabytes written. This is the amount of data the manufacturer rates the drive to handle before reaching its endurance limit. For most people, you're never going to reach that limit. If you ever did, let me know, as you deserve some sort of medal. You can see how much data you've actually written to your SSD by checking the Total Host Writes attribute in CrystalDiskInfo, which is based on the Data Units Written counter for NVMe drives. For example, if your SSD is rated for 600TBW and you've written 60TB, you've used the equivalent of 10% of its rated endurance. Anyway, although I doubt you'll max out your SSD's TBW anytime soon, it shouldn't just straight up die the moment you hit that number. Percentage used Your SSD's health percentage isn't quite what it sounds like This one can be a little confusing, because depending on the tool you're using, you might see it expressed as Percentage Used or Remaining Life. Which, unsurprisingly, will produce wildly different results, so check carefully when you do take a peek. On NVMe SSDs, Percentage Used is the manufacturer's estimate of how much of the drive's rated endurance you've consumed. It starts at 0% and gradually climbs as your SSD wears out. Meanwhile, tools like CrystalDiskInfo will usually show you the opposite, displaying 100% health on a new drive and gradually lowering that number as it ages. As a sidenote, that aging thing is usually pretty slow. My main SSD is nearly three years old and is still sitting at a cushy 96%. Available spare The percentage you shouldn't confuse with free disk space Credit: Patrick Campanale / How-To Geek This one will make you think it's all about how much space you have left on your SSD, and I get it, because it sure sounds like that. But it's actually about that extra storage capacity that exists tucked away and can't be used for your files. This is called spare capacity, and it's there to help the drive deal with NAND flash blocks that become unreliable or wear out over time. On NVMe SSDs, the Available Spare SMART attribute gives you an idea of how much of that reserve remains, expressed as a percentage. In an ideal world, you'll find it sitting at 100%. Watch out for a percentage that keeps dropping, and if it's approaching the Availabl;e Spare Threshold specified by the manufacturer, you might have reason to worry about your SSD. This number can matter more than your SSD's remaining life This is one of the SMART attributes I tend to pay some serious attention to. It sounds bad, and it is bad (if it's not doing well, that is). Media and Data Integrity Errors keep track of instances where your SSD's controller detected an error it couldn't recover from. That can be something like uncorrectable ECC errors or CRC failures. So, what should this number be at? A nice round zero, if possible. If it's above zero, put your detective hat on and start investigating, but more than that, make sure your backups are up to date and start looking for an exit strategy if this counter keeps ramping up. Critical warning Nobody likes the sound of that Credit: Patrick Campanale / How-To Geek The worst of all, Critical Warning. It's ominously named, and aptly so, but I'd bet that for many of you, that value will (hopefully) be sitting at zero or at least close to it. And that's good, because it means none of the drive's defined critical warning conditions are currently active. Anything above zero deserves prompt attention, though. This attribute can flag several different problems, such as spare capacity dropping below threshold, excessive temperatures, degraded reliability, or even the SSD entering read-only mode. It's not a health percentage as much as it is a collection of red flags, and, joy of joys, it'll be up to you to figure out what it means. But the advice remains the same: back up your data to be safe. The best way to keep your data safe is to think ahead When it comes to data, your best bet is to always be a little paranoid, I'm sorry to say. I keep multiple backups of the stuff I truly care about, but I also keep tabs on my SSDs and how they're doing on a regular basis. It takes me two minutes, and while it might not prevent any SSD failures, it could—and that's good enough for me.