A NAS drive failing without warning sounds rare until it happens to you. The real story behind most data loss isn’t a sudden death — it’s months of growing SMART reallocation counts that the owner never bothered to check. These seven apps for disk health monitoring on desktop give you the early warning that turns a planned drive swap into a non-event.
The picks cover the front-line SMART readers, the alerting dashboards for NAS owners, the macOS-specific tools, and the data integrity utilities that catch silent corruption no SMART check can see.
What to look for in a disk health monitor
- Full SMART attribute reading, including vendor-specific values for modern NVMe drives.
- Threshold alerting so you find out before a drive dies, not after.
- Reallocation and pending-sector tracking — these are the values that actually predict failure.
- NVMe-aware decoding for current-generation SSDs (older tools sometimes mis-decode).
- Background monitoring, not just an on-demand scan.
- Free for personal use. The genre has strong open-source options.
- A dashboard or report view if you have more than two drives.
Quick comparison
| App | Best for | Free plan | Starting price | Platforms |
|---|---|---|---|---|
| CrystalDiskInfo | Windows SMART checks | Yes, fully | Free | Windows |
| smartmontools | CLI on every Unix | Yes, fully | Free | Linux/Mac/Win |
| Scrutiny | Multi-drive dashboard | Yes, fully | Free | Linux (Docker) |
| GSmartControl | Linux GUI for smartmontools | Yes, fully | Free | Linux, Win, Mac |
| Hard Disk Sentinel | Windows pro tooling | Trial | About $40 one-time | Windows |
| DriveDx | macOS native | Trial | About $25 one-time | macOS |
| HDDScan | Windows surface scan | Yes, fully | Free | Windows |
| Snapraid | Catch silent corruption | Yes, fully | Free | Linux, Windows |
The apps
1. CrystalDiskInfo, the Windows starting point
CrystalDiskInfo is the Windows utility nearly every NAS forum recommends first. Free, lightweight, and shows every SMART attribute with a Good/Caution/Bad health summary that’s actually useful for non-experts. The 9.x release improved NVMe decoding and added per-drive temperature graphing.
The notification mode runs in the background and pops a warning if a SMART value crosses a threshold. The settings let you tune which attributes trigger alerts — important for SSD drives where the default thresholds can be too aggressive on the wear-level-count.
Pricing:
- Free: Fully
- Paid: None
Platforms: Windows.
Download: CrystalDiskInfo on crystalmark.info
Bottom line: Default to this on Windows. It’s the right starting point for everyone.
2. smartmontools, the CLI standard
smartmontools (the smartctl and smartd commands) is the open-source SMART toolkit that runs on every Unix and most modern Windows installs. It’s the engine many of the GUI tools wrap. If you have a Linux NAS, this is what’s actually reading your drives.
smartctl -a /dev/sda gives you every SMART value on a drive. smartd runs as a daemon and emails you when a threshold is crossed. Configuration is /etc/smartd.conf one-liners; the documentation is comprehensive.
Pricing:
- Free: Fully open source
Platforms: Linux, macOS, Windows (via Cygwin or native package), FreeBSD.
Download: smartmontools on smartmontools.org
Bottom line: Pick this for any Linux box with a drive in it. The smartd email alert is the lowest-effort drive monitoring you can set up.
3. Scrutiny, multi-drive dashboard
Scrutiny is the Docker-based dashboard that wraps smartmontools with a web UI showing every drive in your NAS at a glance. It runs Smartctl tests on a schedule, charts SMART values over time, and integrates with Backblaze’s failure-rate dataset to highlight drives running into known-bad attribute patterns.
The web UI is the differentiator. Compared to smartd’s email-when-broken alerts, Scrutiny shows you what’s getting worse before it breaks. The Notify integration supports Discord, Slack, Healthchecks, email, and more.
Pricing:
- Free: Fully open source
Platforms: Linux (Docker compose). Web UI accessible from any browser.
Download: Scrutiny on GitHub
Bottom line: Pick this for any NAS with more than two drives. The Backblaze-trained alerting catches drives most other tools miss.
4. GSmartControl, Linux GUI
GSmartControl is the cross-platform GUI for smartmontools. It exposes the full smartctl feature set in a friendly window, including the ability to run short and long self-tests, view per-attribute graphs, and copy reports for forum posts.
This is the “I want to check a drive once” tool, not the “monitor every drive forever” tool. If you don’t want a daemon and just want to verify a drive is healthy before you trust it with data, GSmartControl is fast.
Pricing:
- Free: Fully open source
Platforms: Linux, Windows, macOS.
Download: GSmartControl on gsmartcontrol.shaduri.dev
Bottom line: Pick this for one-off drive checks on Linux or for occasional Windows use.
5. Hard Disk Sentinel, Windows pro tooling
Hard Disk Sentinel is the paid Windows tool that goes furthest into drive analysis. The health-percentage estimate is more nuanced than CrystalDiskInfo’s Good/Caution/Bad, and the surface-scan tools are robust. The trial gives you a sense of whether the depth is worth the $40.
The Pro version’s automatic backup trigger (start a copy job when a drive’s health drops below a threshold) is the feature that justifies the price for people storing irreplaceable data on aging drives. The temperature alerts and acoustic monitoring are bonus.
Pricing:
- Free: Trial (limited features)
- Paid: About $40 (Standard); about $80 (Pro)
Platforms: Windows.
Download: Hard Disk Sentinel on hdsentinel.com
Bottom line: Pick this if you’re storing data you can’t replace on aging drives and you want the most thorough Windows tool.
6. DriveDx, macOS native
DriveDx is the most thorough SMART tool on macOS. macOS’s built-in Disk Utility is too sparse to give you real SMART data; DriveDx fills the gap with full attribute decoding for SATA, NVMe, and even external USB-connected drives that other macOS tools can’t see.
The 1.12 release added Apple Silicon native support and improved external-drive detection over USB-C. The 28-day free trial is enough to evaluate.
Pricing:
- Free: 30-day trial
- Paid: About $25 (Personal); about $50 (Pro for multi-Mac use)
Platforms: macOS.
Download: DriveDx on binaryfruit.com
Bottom line: Pick this on macOS. The built-in Disk Utility’s SMART data isn’t usable.
7. HDDScan, Windows surface scan
HDDScan is the free Windows tool for low-level scans: bad-sector mapping, read-write verification, and the kind of testing that CrystalDiskInfo’s quick-look doesn’t do. Pair this with CrystalDiskInfo and you have a Windows-side stack that covers both “is the SMART data clean” and “is the actual physical surface okay.”
The interface is utilitarian and hasn’t changed much in years, which is fine for a tool you run when you suspect a problem. The HDDScan output is also useful evidence for an RMA claim with a drive manufacturer.
Pricing:
- Free: Fully
Platforms: Windows.
Download: HDDScan on hddscan.com
Bottom line: Pick this for any Windows drive you suspect has bad sectors. Free, fast, gives you the evidence to either trust the drive or RMA it.
8. Snapraid, catch silent corruption
Snapraid isn’t a SMART tool — it’s the layer that catches what SMART misses. Silent data corruption (a bit-flip on a healthy drive) doesn’t trigger any SMART alert because nothing failed at the drive level. Snapraid computes parity from your data and catches mismatches on a scheduled scrub.
For a home media archive where you can tolerate a daily sync delay (rather than running ZFS or btrfs with real-time RAID), Snapraid is the simplest way to add bit-rot detection. Pair it with smartmontools and you cover both predicted-failure and silent-corruption.
Pricing:
- Free: Fully open source
Platforms: Linux, Windows (and macOS via build-from-source).
Download: Snapraid on snapraid.it
Bottom line: Pick this for a media archive on aging drives. SMART catches drive-side decay; Snapraid catches everything else.
How to pick the right one
If you want to start checking your drives today on Windows: CrystalDiskInfo. Install, look at the Good/Caution/Bad indicator, set up the background alert.
If you have a Linux NAS: smartmontools as the engine, Scrutiny as the dashboard. The smartd config takes ten minutes.
If you have a Mac: DriveDx. The built-in tools are not enough.
If you store data you cannot replace: Hard Disk Sentinel Pro on Windows or Scrutiny on Linux, plus Snapraid for silent corruption coverage.
If you just want to check one drive once before trusting it: GSmartControl. Run a long self-test and read the report.
FAQ
How often should I check disk health?
Background monitoring (smartd, Scrutiny, CrystalDiskInfo’s notification mode) should run continuously. Active scrubs (Snapraid, surface scans) once a month is reasonable for a media archive.
Which SMART attribute matters most?
For HDDs: Reallocated Sector Count, Pending Sector Count, and Uncorrectable Sector Count. Any non-zero value on a young drive is a warning sign. For SSDs: Wear Leveling Count and Reallocated NAND Block Count. Modern SSDs also expose a Percentage Used Endurance Indicator.
Can I trust the manufacturer’s “drive health” utility?
Sometimes. Western Digital’s Dashboard, Samsung’s Magician, and Seagate’s SeaTools each have value for firmware updates, but they aren’t substitutes for cross-vendor monitoring. Most users keep CrystalDiskInfo or smartmontools as the daily checker.
Will SMART catch every failure?
No. Sudden electronic failures (a bad controller chip, a power surge) can take a drive out with zero SMART warning. SMART catches the slow degradation, which is most failures but not all. This is why backups exist.
Are Blu-ray and DVD actually better for long-term storage?
For cold storage, yes. M-Disc rated Blu-ray and DVD have lab-validated 1000+ year archival ratings, while consumer SSDs lose data after roughly five to ten years without power. For active storage with SMART monitoring and backups, drives are fine — but for “I want this still readable in 2050,” optical media is the better bet.
