Disk Drives

This includes both physical drives and virtual drives. Physical drives can be internal or  external, magnetic or solid state, IDE, SCSI, SATA, SAS, USB or just about any connection.

Disk drives have a partition structure.  This is also known as a volume structure. Each partition or volume also has a file structure.

Not all Operating Systems (OS) read all partition structures or file structures.  A blank drive in onc system can have a unsupported format from another system.

File Structure Types


FAT stands for File Allocation Table and comes in three main versions FAT, FAT16 and FAT32 found in DOS the precursor to Windows.  The difference between versions is how many files and how large the disk can be.

FAT32 had a maximum partition size of 2TB but the file size limit was 4GB.

Found in DOS and Windows, it can be seen on USB drives and most OS can read it.


NTFS stands for New Technology File System.  Yep Microsoft NT stands for “New Technology”.  It been around since 

The max partition size, number of files and file size has changed over the years

Operation System (OS)Vol SizeFile SizeMax Files
Windows 7 or earlier
Server 2008 R2 or earlier
256TB16 TB4.294 Billion
Windows 8 or 8.1
Windows 10 (build 1703 or earlier)
Server 2012, 2012R2, 2016
256TB256TB4.294 Billion
Windows 10 (build 1709)
Server 2019
8PB8PB4.294 Billion


As disks age they develop problems, some are fixable by the system while others are not.  In some cases its possible to send a drive to a clean room facility and perform recovery.  I recommend Ontrack Data Recovery if you need that level of support.

There are several utilities provided by to locate bad file structures, bad sectors and perform recovery.

Time need run these utilities varies with size of disk and if it finds a problem.  This could be 5 minutes to over 12 hours.

For the Do It Yourself crowd.


For a more complete guide see this HOWTO guide.

Built into every version of Windows since the days of DOS.  Has been updated with every version of Windows.  Since Windows 7 the basics have not changed.

Works on FAT, NTFS, …

Two modes

  • Online scan. This leaves the disk online and does a basic check. It will not locate bad sectors.
  • Offline scan. This will offline the disk to lock it exclusively for the disk check. This is how to scan for bad sectors.
    • If you do this check on the boot partition it will require a system reboot.
    • For boot partition the information is saved to the Application Event log.

Detail information is saved to the Application Event log but summary information is typically shown on screen. The command line can be piped to a text file.

GUI Usage

Two check boxes are available. “Automatically fix file system errors” and “Scan for and attempt recovery of bad sectors”.

Without either option check the scan is informational.

If “Automatically fix file system errors” is check the system will attempt to fix file structure errors.  If it can’t it will often truncate bad files resulting in file corruption and/or data loss.

If the “Scan for and attempt recovery of bad sectors” is checked the system will search and mark new bad sectors as unusable.  If possible it will move an recoverable data to a new location.

Command Line Usage

Open an admin-mode console to run the command.  If you don’t insert a drive letter or mount point the command will run on the current disk.

The basic command structure is

CHKDSK <Volume> <options>

Replace <Volume> with your drive letter and remember to have the “:” immediate after the letter.  It is possible to check mount points.


  • /scan or /scannow only scan don’t fix
  • /f to fix file structures
  • /r to search for bad sectors
  • /x to perform an exclusive offline scan

Without the /x option it is possible for CHKDSK to miss some errors.

The command I use most often

CHKDSK <Volume> /x /r /f

Clean Room Services

Sometimes when you have to recovery whatever you can.  In my lifetime of IT experience I’ve seen a few people forced to take this option.

Ontrack Data Recovery Service is the go to operation.  The first time I saw a client use them was for a fire.  The hard drives where in a fire safe but the fire was so hot it toasted the drives.  Ontrack recovered over 80% of the data.

Third Party recovery Tools

When your disk drive isn’t giving you anything it might be possible to recover the data yourself using a 3rd party tool.  As long as there is not a physical issue with the drive mechanics a partial recovery of data should be possible. 

Your mileage may vary and use these at your own risk.

These tools are not quick and can take several hours to complete before you know if the data can be recovered.


One of the better recovery programs.  I’ve used this the most.  They also have several other data recovery solutions for the Do-It-Yourself person if you have a RAID or NAS that needs advanced recovery.

Ontrack Data Recovey Software

Same company that does the clean room restoration work sells recovery software.


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