Reallocated Sectors Count: What It Means For Your Hard Drive

If S.M.A.R.T data for your hard drive is showing a number other than 0 next to “ID 05 Reallocated Sector Count”, I’m going to be up front and let you know that this isn’t a good sign. Increases in reallocated sectors are one of the tell tale signs of a drive that’s dying – do not ignore the warnings.

Let’s cut to the chase with a quick 5 point summary:

  1. Reallocated sectors are bad sectors on your hard drive that have been moved to another part of the disk
  2. There is no fix to lower your reallocated sector count
  3. Backup your data (now and always)
  4. If your data is important to you, you should buy a new hard drive
  5. Or: If your hard drive is still under warranty, send it in for a replacement (but back it up first)

If this list made you panic, I apologize. Depending on your specific situation, things may not be that bad. But you should seriously read #3 again, that one’s relevant to everyone.

If you’re looking for tools to check your current reallocated sector count you can jump down to ‘How to check for reallocated sectors’

What are reallocated sectors?

Reallocated sectors are parts of your hard drive’s platter that can no longer be trusted to safely store data. Each sector is quite small, holding just 512B (bytes) of data. When your hard drive encounters an error while reading, writing or verifying data it marks the sector as reallocated and then moves the data to a reserved area on the disk (spare sectors that it sets aside). This is a normal part of a hard drive’s operation that’s done to prevent data loss and corruption.

Essentially your hard drive has noticed a problem with a part of the disk and rather than saving your data there with a risk of it getting corrupted, it moves the data to a safe part of the disk and continues on with what it was doing. Even though sectors are quite small, if you were to lose a sector that contained part of a bigger file like a photo, video or word document – you may no longer be able to open those files because a chunk of them is missing.

Reallocated Sectors and Hard Drive Failure

A reallocated sector count above zero does not immediately tell us whether or not the hard drive is doing to fail, but it can be an early warning sign. If your drive has 1, 2 or even a couple dozen bad sectors it may go on to live many more years and work fine. The warning sign that can tell us if a drive is failing is how quickly your reallocated sector count grows.

Let’s say 2 reallocated sectors pop up in your S.M.A.R.T monitoring tool, and after a few weeks your count is still at 2. This *may* not be a big problem. I’ve seen many hard drives that ran fine for years with a handful of reallocated sectors, but if your reallocated sector count continues to go up you should replace your drive immediately.

Is it safe to keep using my hard drive?

Maybe. It really depends on how valuable your data is to you. If you’re using the hard drive for testing purposes or don’t have anything important stored on it, you have my permission to keep using that drive. But If your data is important to you and this is the hard drive in your primary computer, I would suggest replacing it.

I’ve had a friend ask “How many reallocated sectors is too many?” and my immediate answer was “1”. My data is extremely valuable to me, so if I see any reallocated sectors pop up I immediately start making an additional local copy of the data and order myself a brand new drive. I’m not much of a risk taker, I’d rather have to spend some money for a new drive than risk the drive failing spectacularly or silently corrupting my data.

Backup Your Data, Right Now

All hard drives will eventually fail, but S.M.A.R.T data is your warning sign so take it seriously and immediately make a backup of your important data if you’ve noticed reallocated sectors.

Hard drives can fail in many ways: the motor can fail, the head can scratch the disk or there may be a manufacturing defect that results in a bunch of bad sectors. You should ALWAYS make sure you have a recent backup of your data saved on an external drive or with a cloud storage/backup provider. Hard drive failures occur suddenly and data recovery from failed drives can be extremely costly – ranging from a few hundred dollars to 10s of thousands, or in the worst cases: the data isn’t recoverable at all.

Fixing Reallocated Sectors

The only “fix” for a reallocated sector is to purchase a new hard drive. Once a sector has been reallocated the hard drive will no longer use it and will continue operation without storing data on that part of the disk. There is no software or hardware fix to lower your reallocated sector count.

I’ve seen some horrifying YouTube videos of people opening up hard drives to “fix” reallocated sectors. Please, whatever you do, DO NOT OPEN YOUR HARD DRIVE. All that is likely to happen is you’ll end up with a hard drive-sized paper weight. Sectors are microscopic and there are a million ways for them to go bad, opening a hard drive outside of a clean room without professional experience in data recovery is only going to create more problems. You’re almost guaranteed to introduce dust or break it in some way.

Only after you backup your data and purchase a new drive can you crack it open and turn the platters into some sweet drink coasters.

RMA’ing A Drive With Reallocated Sectors

If your drive is still under warranty you can initiate an RMA (warranty return process) with the manufacturer. You’ll be asked to ship in the drive and usually within a couple weeks they’ll ship a different drive back to you. RMA drives can sometimes be brand new, but most of the time the hard drive maker is going to send you a refurbished drive that has passed their testing process.

Checking your warranty: Enter your drive’s serial number (located on top of the drive) into the warranty checker for your hard drive’s manufacturer. If you don’t know who makes the drive you can find it (and the serial number) using the tools linked at the bottom of this page. Here are the links to check your warranty with the biggest hard drive manufacturers:

Backup your data before you send in your drive! You will not get the same drive back. Your hard drive maker will ship you a (usually) refurbished hard drive from their stock that is completely wiped clean. They will not ship your drive back to you if you forget to back something up.

Reallocated Sectors Can Slow Down Your Hard Drive

If you’ve read most this article, understanding the risks associated with a climbing reallocated sector count, and you’re going to continue using your hard drive you should know that many reallocated sectors can slow down your drive by 10% or more. When your hard drive is reading data off it’s disk and encounters a reallocated sector it needs to take a trip off the beaten path to get the moved data. If you have a small handful of reallocated sectors you probably won’t notice any speed changes, but if your drive is showing many reallocated sectors you will notice a slow down.

How to check your reallocated sector count


If you run Windows you can install CrystalDiskInfo (free) which will give you a detailed report of S.M.A.R.T data for every drive in your computer. It’s one of the first things I install on a PC so I can easily monitor my hard drive health. You can download it from the CrystalMark website.

CrystalDiskInfo ID 05 Reallocated Sector Count 100
Most people misread CrystalDiskInfo output, the column you want to look at is ‘Raw Values’. By default this is hexadecimal but you can change this to a standard number by clicking on Function -> Advanced Features -> Raw Values and setting it to ’10 DEC’.


MacOS comes with a piece of software called Disk Utility which can show you the current S.M.A.R.T status of drives inside your Mac. Unfortunately it doesn’t give you much more info than whether or not your drive is ‘Verified’ (fine) or ‘Failing’.

On a Mac you can use an application called DriveDx to check your reallocated sector count. A full version of the application costs $19.99 but the free trial works fine if you just want to quickly check, you can download it from the DriveDx website.

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