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Fix Service Host SysMain High Disk Usage

Service Host SysMain causing 100% disk usage? Find out how to fix that

Previously, many Windows 10 users had issues with the Superfetch service causing high disk usage. But this service was replaced with a service called SysMain, which is the same service but with a new name. Many people have noticed that SysMain uses way more disk resources than it normally should, making their computers run considerably slower. This article will help you address this issue by providing you with ways to fix SysMain high disk usage.

In addition to RAM, Windows also has a paging file (virtual memory). Virtual memory space is reserved on the hard disk, which allows loading memory and storing information. When there’s not enough RAM, programs that need it may access virtual memory found on the hard disk. Page file memory was first introduced in Windows Vista under the name Superfetch.

In the Windows 10 update 1809, Microsoft replaced the Superfetch service with SysMain. So, after Windows 10 version 1809, when the system needed more memory than was available, instead of sending data to the paging file on the hard disk, it compressed the data. So a 2GB package can be compressed into a 1GB package. In short, SysMain analyzes your application usage patterns and optimizes program launching.

SysMain is part of the Service Host bundle of services. Service Host includes many other services, such as Local System (Network Restricted), Local Service, Network Service, Windows Update, and so on.

SysMain was designed to preload applications to all available (unused) RAM space. Before Windows 8.1, if an application needed more RAM than a computer physically had, then the data that couldn’t be loaded to the RAM was sent to the paging file, which is on the hard drive. This virtual memory type made it possible to launch and run resource-intensive applications, though they worked noticeably slower.

So, in addition to regular memory known as RAM, Microsoft Windows also utilizes virtual paging file memory (Superfetch) or compressed memory (SysMain.)

As previously mentioned, Superfetch and SysMain are basically the same things, but SysMain was introduced in Windows 10 and is a better alternative to the paging file, improving overall performance. Unlike Superfetch, which can be enabled and disabled, SysMain is enabled by default in Windows 10.

SysMain was designed to maximize memory and keep your PC running smoothly even during high-intensity workloads. SysMain analyzes RAM usage and monitors which applications are used most frequently. Then, it preloads the most commonly used applications into the RAM to start them faster when needed, which is said to be superior to conventional virtual memory used in Windows 8, 7, and earlier versions.

Fix Service Host SysMain high disk usage

Nevertheless, Windows 10 is designed to avoid using SysMain whenever possible. However, when there’s a need for a large amount of memory, Windows initiates the SysMain service.

While SysMain is much better than Superfetch in terms of performance, it still has the same issue as Superfetch, which is high disk usage. Under certain conditions, SysMain may start using 100% of your disk, which significantly degrades your computer’s overall performance.

Since SysMain is responsible for maintaining and improving system performance, it collects data of every kind of usage on the system. The service then reorganizes the data in the form of blocks for the disk and prioritizes the data accordingly.

SysMain is likely to give you trouble, especially if you’re using an HDD on your PC. HDDs are slower to reorganize than SSDs, which may result in high disk usage.

Furthermore, high disk usage may not be your only problem. As a result of high disk usage, SysMain ends up using all of your remaining CPU power. Therefore, when you open Task Manager, you may notice your disk or CPU usage at 100%. Ironically, SysMain, which is meant to optimize your computer’s performance, may slow it down to a crawl.

The SysMain service causes high disk usage, so what’s the big deal? By hoarding your disk’s resources, SysMain slows down your computer, making it slow to respond to commands and, in some cases, makes your PC nearly impossible to use.

So if you’re experiencing the problems mentioned above, then you ought to disable SysMain altogether. The good news is that disabling it won’t noticeably impact your computer’s speed and overall performance.

We have compiled a list of ways you can disable SysMain, including stopping and disabling the SysMain service in the Services Manager or using the Command prompt. You may also disable the service in the Registry Editor. If you want to enable SysMain again later, we recommend doing that after a Windows update, which fixes the high disk and CPU usage issue.

Table of Contents:

Option 1. Disable SysMain using Windows Services Manager

1. Hold down Windows+R keys to open the Run dialog box.

Type in Services.msc and click OK

2. In the Run text box, type in Services.msc and click OK.

Right-click SysMain and click Properties

3. Scroll through the services list and locate SysMain.

4. Right-click SysMain and click Properties.

Click Stop under Service status

5. Once in SysMain Properties, click the Stop button under the Service status section.

Click Disabled under Startup type

6. Then, Under the Startup type setting, open the drop-down menu and select Disabled.

Click Apply and click OK

7. Click Apply and click OK.

SysMain is now stopped and will no longer launch on system startup.

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Option 2. Disable SysMain using Command Prompt

1. Hold down Windows+R keys to open Run.

Type in CMD and open Command Prompt in elevated mode

2. Type in CMD in the Run text box and hold down Shift+Ctrl+Enter keys to open the elevated Command Prompt.

Enter command to disable SysMain via Command Prompt

3. In the Command Prompt window, type in sc stop “SysMain” & sc config “SysMain” start=disabled and hit the Enter key. You should get a ChangeServiceConfig SUCCESS message.

Close the Command Prompt and open Task Manager to check if disk/CPU usage has gone down.

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Option 3. Disable SysMain using Registry Editor

1. Hold down Windows+R keys to open Run.

Type in regedit in Run and click OK

2. In the Run text box, type in Regedit and click OK.

Navigate to SysMain in the Registry Editor

3. Once in the Registry Editor, navigate to KEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SysMain

Right-click the Start and click Modify

4. In the right pane, right-click Start and click Modify.

Enter the number 4 in the Value data text box and click OK

5. In the Value data text box, type in 4.

6. Click OK to save the changes.

Close the Registry Editor and open Task Manager to check if disk/CPU usage has gone down.

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Option 4. Run Windows Update

Updating Windows may help in fixing SysMain’s high disk usage. Microsoft periodically releases updates that fix bugs, improve system stability, and optimize system performance, so updating Windows is one of the easiest things to do if you want to resolve your high disk usage issue.

Right-click Start and click Settings

1. Right-click the Start Menu button and select Settings.

Select Update & Security

2. Then, select Update & Security.

Click Check for Updates

3. Click the Check for updates button.

Click Install now

4. If Windows has already checked for updates, click the Install now button.

5. Wait for Windows to download and install the latest updates. Note that the update may take some time, and you will have to restart your computer to finish installing the updates.

Click Restart now

6. Then, click Restart now when prompted, and allow your PC to reboot.

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About the author:

Tomas Meskauskas

I am passionate about computer security and technology. I have an experience of 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an editor for pcrisk.com since 2010. Follow me on Twitter to stay informed about the latest tech news or online security threats. Contact Tomas Meskauskas.

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