Here you can know what defragment disk is and how to defrag disk and check your hard disk with AOMEI Partition Assistant.
You are in the middle of reorganizing your hard drive—perhaps extending your C drive or resizing a data partition—using AOMEI Partition Assistant. Suddenly, the operation stops, and you are greeted with an error message (often Error Code 205 or similar) suggesting you need to "Defragment" or "Check and Fix" the partition before proceeding.
This error can be frustrating, but it is a safety mechanism. Partition software works by physically moving data blocks to new locations on your drive. If the file system contains errors (bad sectors) or if the files are scattered in thousands of tiny pieces (fragmentation), the software cannot move them safely without risking data corruption. Therefore, it halts the operation to protect your files.
In this comprehensive guide, we will walk you through exactly how to check your disk for errors and how to properly defragment your drive (and when not to), so you can resume your partition operations successfully.
File system errors or "bad sectors" are the most common reason partition operations fail. These are small spots on the disk that are unreadable or corrupted. Before resizing, you must repair them.
You don't need to leave the software to fix this. AOMEI Partition Assistant includes a built-in diagnostic tool that interfaces with Windows' check commands.
Right-click the Partition: In the main AOMEI interface, right-click the partition that gave you the error (e.g., C: drive).
Select Advanced: Go to Advanced > Check Partition.
Choose Mode: Select the first option: "Check partition and fix errors in this partition using chkdsk.exe".
Run: Click OK. If checking the system drive, it may ask to reboot into PreOS mode. Allow it to do so. The software will automate the repair process.
If you prefer using native Windows tools, the chkdsk command is the gold standard for disk repair.
Press Windows + R, type cmd, and press Ctrl + Shift + Enter to run as Administrator.
Type the following command (replace C: with the target drive letter):
chkdsk C: /f /r
Explanation of Commands:
/f: Fixes logical errors in the file system.
/r: Locates bad sectors and attempts to recover readable information.
If the volume is in use (like the C drive), type Y to schedule the check for the next restart, then reboot your computer.
If checking for errors didn't solve the issue, your drive might be heavily fragmented. Fragmentation happens when a single file is broken into pieces and scattered across the disk platter. Partition software needs contiguous free space to operate, which fragmentation prevents.
⚠️ Critical Warning: HDD vs. SSD
Before you defrag, you must know what type of drive you have.
HDD (Hard Disk Drive): DO defragment. It organizes data and speeds up the drive.
SSD (Solid State Drive): DO NOT defragment. SSDs do not use spinning platters. "Defragging" an SSD performs unnecessary write cycles, reducing its lifespan. If you have an SSD, simply running a "Check Partition" is usually enough; skip the defrag step.
Type "Defrag" in the Windows search bar and select "Defragment and Optimize Drives".
Select the drive you want to fix.
Click Analyze (if available) to see the fragmentation percentage.
Click Optimize. Windows will automatically defrag an HDD or run the TRIM command for an SSD.
AOMEI Partition Assistant Professional offers a "Disk Defrag" feature that is often faster and more intelligent than the Windows default.
In AOMEI Partition Assistant, click on "Disk Defrag" in the left menu or tools list.
Check the partition you want to analyze.
Click Analyze. The software will give you a score.
If fragmentation is high, click Defrag.
Note: AOMEI will automatically detect if the drive is an SSD and prevent traditional defragmentation to protect your hardware.
You might wonder, "Why does the software care if my files are messy?"
Imagine you are trying to shrink a partition. You need to chop off the space at the end of the partition. However, if your hard drive is fragmented, bits of data might be sitting at the very end of the drive, blocking the "chop."
To shrink the partition successfully, AOMEI Partition Assistant must first identify these scattered files. If they are too fragmented, the software cannot safely calculate where to move them. By running a defrag (on HDDs), you pack all the data tightly to the beginning of the drive, leaving a clean, continuous block of free space at the end that can be easily manipulated.
The error prompting you to "Defragment or Check and Fix Partition" is not a malfunction; it is a safeguard. It ensures your data structure is healthy and organized before performing heavy-duty resizing operations.
♦Q: Can I use the computer while CHKDSK is running?
A: No. If CHKDSK runs on boot, you must wait for it to finish. If you run it inside Windows on a non-system drive, the drive will be inaccessible until the scan finishes.
♦Q: How long does a defrag take?
A: It depends on the size of the drive and the level of fragmentation. It can take anywhere from 15 minutes to several hours.
♦Q: I have an SSD, but I still get this error. What should I do?
A: Do not defrag the SSD. Run the chkdsk /f /r command (Part 1). If the error persists, ensure you have disabled "Fast Startup" in Windows or try resizing the partition in smaller increments.