When you run into data drive issues on Windows, the first thing you should do is run CHKDSK ("check disk"). It's one of the more useful diagnostic tools on Windows, and it's part of the operating system itself so you don't need to install anything.

Long story short, CHKDSK scans a drive volume and verifies that the file system's integrity hasn't been compromised -- and if it spots any logical errors, it will fix them. It won't be able to fix everything, such as if your hard drive is physically dying, but it's a good place to start.

We've already written about how to use CHKDSK so hop over there if you just want to get started. This post is about how the CHKDSK tool in Windows 8 and 10 is a vast improvement over what CHKDSK used to be in Windows 7.

Online Scan

        /scan
    

This switch only works on NTFS drives.

Normally when a drive is scanned and found to be in need of fixing, it must first be dismounted. Since system drives can't be dismounted while the system is running, this means that you can only fix them prior to booting up. Non-system drives aren't beholden to this issue.

With Windows 8, and thus also in Windows 10, a new feature called self-healing was introduced that made it possible for certain types of issues to be fixable without needing to dismount the drive. That's why it's called "online scan": it doesn't involve the internet at all, but rather lets your drive stay online while being fixed.

Note that many drive-related issues still can't be fixed this way, so if the online scan doesn't help at all, you should immediately run a full offline scan to make sure CHKDSK covers everything it can.

external-hard-drive-laptop
        /forceofflinefix
    

This switch must be used at the same time as the online scan switch. When used, it bypasses all online repairs and instead queues all of the found errors for offline repair.

        /perf
    

This switch must be used at the same time as the online scan switch. Since the online scan runs while the system is operating, it doesn't scan at full power (so that your system doesn't slow down to a crawl). Use this switch if you want a faster scan, but know that it may impact your system's speed.

Spot Fixing

        /spotfix
    

This switch only works on NTFS drives.

Windows 8 and Windows 10 both have system-level maintenance tasks that run in the background at various points throughout the day. When these tasks encounter errors or corruptions, they are logged into the system so that they can be fixed later.

Spot fixing, then, is a switch that runs CHKDSK so that it only goes through these logged errors and corruptions, and it will immediately fix the ones that it can fix. This is much faster than normal as it doesn't require scanning the entire drive.

hard-drive-internals-close-up

Free Up Ophaned Cluster Chains

        /freeorphanedchains
    

This switch only works on FAT/FAT32/exFAT drives.

FAT-based drives divide the space into contiguous chunks of storage that are used to store files, and each of these chunks is called a cluster. All clusters are tracked with an index table, giving FAT its name: File Allocation Table.

When multiple clusters are needed to store a file, table entries have pointers that point to the next cluster in the chain.

But sometimes errors occur and these chains are broken. Maybe one cluster gets erased and marked as "unused" but its subsequent clusters get missed -- thus leading to clusters that are marked "used" but can't ever be accessed. These are called orphaned.

This CHKDSK switch simply locates all orphaned clusters and frees up their data.

Mark Drive as Clean

        /markclean
    

This switch only works on FAT/FAT32/exFAT drives.

Sometimes a drive's dirty bit won't be cleared, even though no corruption or issues were found. This can be a nuisance, as it causes CHKDSK to run every time the system is rebooted. This switch will manually mark the drive as clean.

Cortana Integration

"Integration" is a pretty strong word to use for this modest feature, but it is what it is so let's run with it. If you have Cortana enabled on Windows 10, you can bypass the Command Prompt altogether by typing the CHKDSK command straight into Cortana.

cortana-chkdsk-command-run

CHKDSK May Not Be Enough

As useful as CHKDSK is, you should know that it isn't perfect and it isn't the only tool that you should rely on. Check out our full exploration of proper maintenance in Windows 10 so that you know what to do when something goes wrong on your system.

If your drive is corrupted or brkoen in an irreparable way, note that you may still be able to recover the data on the drive. If you ever find yourself in such a position, check out these free data recovery tools. Don't underestimate the importance of data backups!

And if your drive is dead, there really isn't much you can do except to replace it. For drives meant for long-term storage, we recommend buying a hard disk drive. For drives meant to run an operating system, we recommend buying a solid state drive.

For more Windows knowledge, here's the difference between CHKDSK, SFC, and DISM.

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