How to Read Hard Drive S.M.A.R.T Data

Modern hard drives use S.M.A.R.T (Self-Monitoring, Analysis, and Reporting Technology) metrics to forecast hardware failures. 

A hard drive with severely damaged platters.

In most cases, home computer users don’t need to worry about S.M.A.R.T data — but if your hard drive seems to be operating at slow speeds, data is becoming corrupt, or you notice other symptoms of an impending hard drive failure, S.M.A.R.T analysis can provide useful information. 

In this article, we’ll explain how to access S.M.A.R.T in Windows and Mac OS X, then provide some tips for interpreting the data.

Before we get started, an important note: If you believe that your hard drive is failing, back up important data before taking any additional steps. If the symptoms are severe (missing files, clicking sounds, or other signs of mechanical failure), we strongly recommend working with an experienced data recovery provider — running the hard drive, even for a few seconds, may cause permanent data loss. 

With that in mind, here’s how to read S.M.A.R.T data and make sense of the numbers.

Accessing S.M.A.R.T Data in Windows

You can get basic S.M.A.R.T data through Windows’ Command Prompt, through disk health utilities that came with your hard drive, or through open-source tools like CrystalDiskInfo. 

While you can pay for utilities that read S.M.A.R.T info, you don’t need to do so — free utilities will give you enough information for most purposes. 

To access S.M.A.R.T data via the Command Prompt: 

1. Open the Start menu. 
2. Type cmd in the search box. Right click the Command Prompt and select Run as Administrator.
3. Type wmic and press Enter.
4. Type diskdrive get status and press Enter.

This will result in a simple output: If the drive is failing, the prompt will display Bad, Caution, or Unknown. If the drive is healthy, the prompt will display OK.

While this gives you a quick idea of your hard drive’s health, it won’t display detailed metrics — to see those numbers, install CrystalDiskInfo or a similar utility.

Accessing S.M.A.R.T Data in Mac OS X

You can view S.M.A.R.T data in Mac OS X through the System Report menu. Once again, this is basic info: You’ll only be able to determine whether or not the device is failing.

To view the info:

1. Click the Apple icon in your menu bar.
2. Select About This Mac from the drop-down menu.
3. Select System Report.
4. Select SATA/SATA Express from the hardware menu on the left side of the screen.
5. Look for S.M.A.R.T. Status. 

The display will show Verified if the hard drive is working as expected. If the drive is failing, the display will read Failing.

To view more detailed S.M.A.R.T data, you’ll need to install the free open-source tool smartmontools, available here. After installing the utility, open the Mac OS terminal, then follow these steps:

1. Enter diskutil list. 
2. Note the disk index of the hard drive(s).
3. Enter smartctl -a /dev/disk0, replacing disk0 if necessary with the correct identifier from the disk index.

This will display additional S.M.A.R.T attributes.

Reading Detailed S.M.A.R.T Attributes

If you simply want to determine whether your hard drive is failing, you should have your answer by this point — but if you’re a nerd (like us), you might want some additional info. 

By digging through S.M.A.R.T attributes, you can get more information. However, it’s important to note that different hard drive manufacturers have different methods for expressing S.M.A.R.T attributes; avoid drawing broad conclusions about the data.

S.M.A.R.T attributes are expressed through ID numbers and hex codes, with set thresholds that indicate whether each metric is within a “healthy” range. For a full list of known S.M.A.R.T attributes, see NTFS.com’s S.M.A.R.T Attributes page.

Some especially important attributes:

• 01, “Read Error Rate” – This indicates the number of hardware read errors. A lower number is better.
• 02, “Throughput Performance” – This indicates the general throughput performance of the hard drive. A higher number is better.
• 05, “Reallocated Sectors Count” – Indicates the number of sectors that have been reallocated, or remapped. A lower number is better.
• 07, “Seek Error Rate” – Indicates the rate of seek errors of the magnetic heads. Seek error rates may rise due to damage to the actuator heads, platters, or electronics. A lower number is better. 

Once again, this is not a comprehensive list. Any S.M.A.R.T error is a serious indicator of an impending hard drive failure — which is why most computer users should simply check whether a drive is “OK” or “Failing,” then take their next steps based on that information.

Related: Hard Drive Seek Error Rate What It Means (And Why It Matters)

Should I back up a hard drive with a S.M.A.R.T warning? 

Ideally, you’ll have a comprehensive backup strategy in place, and when you receive a S.M.A.R.T warning, you’ll simply need to replace the hard drive with another storage device.

Rotational damage to hard drive platters.

In the real world, data loss can strike at inopportune times. If you don’t have a backup of important files, you may be able to make a backup from your failing drive — but exercise caution.

• If the hard drive is failing, operating the drive for any amount of time could make the problem worse.
• If the hard drive is already experiencing seek errors, you may not be able to retrieve an uncorrupted copy of important files. 
• Attempting to fix a hard drive with S.M.A.R.T errors is not recommended. Running chkdsk (checkdisk) or similar utilities could cause the hard drive to mark readable sectors as “bad,” or could prompt a head crash if the drive’s actuator assembly is already failing. 

The safest course of action is to get your hard drive to a qualified data recovery provider. While data recovery can be expensive, it’s generally quite affordable when the drive is in an early stage of failure — technicians can safely clone the drive in a controlled environment while monitoring for signs of failure. 

At Datarecovery.com, we provide free media evaluations and support all of our services with a no data, no charge guarantee: If we’re unable to recover the files you need, you don’t pay for the attempt. 

We believe that our approach helps consumers avoid data loss while limiting expenses — and hopefully, provides a cost-effective option for restoring essential data during the early stages of hard drive failure.To learn more, call 1-800-237-4200 to speak with an expert or schedule a risk-free evaluation online.