What is mds_stores on Mac & Why It Causes High CPU Usage

If you‘ve ever opened Activity Monitor on your Mac and noticed the "mds_stores" process using a lot of CPU, you may be wondering what it is and whether it‘s cause for concern. mds_stores is part of the Spotlight search feature on macOS, and while it‘s a key part of keeping searches fast, it can sometimes bog down your system. In this article, we‘ll take an in-depth look at what mds_stores does, why it can cause high CPU usage, and most importantly, several ways to fix the problem.

Understanding the mds_stores Process

mds_stores, which stands for "metadata server stores", is an important part of the Spotlight search engine on Mac. Spotlight allows you to very quickly look up files, folders, apps, and other content on your computer. In order to provide lightning-fast search results, Spotlight needs to constantly index and catalog all the files on your hard drive, along with metadata like file names, types, contents, and attributes. This is where the mds_stores process comes in.

Imagine you have thousands of files on your Mac. Having to search through each one individually to find what you‘re looking for would be extremely slow. What mds_stores does is create and maintain an index database of all that file info ahead of time. So when you do a Spotlight search, instead of scanning every file, it just looks up matches in its pre-built index, allowing results to come back almost instantly.

The mds_stores process is constantly running in the background, monitoring your hard drive for new, modified, and deleted files and updating its database accordingly. For the most part, this happens quietly without any major impact on CPU usage. However, there are times when mds_stores can start consuming a lot of processing power.

Why mds_stores Can Cause High CPU Usage

While mds_stores usually hums along unobtrusively in the background, there are a few common situations that can cause it to suddenly start using a lot of CPU cycles:

Indexing a large number of new files – If you copy a big folder of files to your hard drive, add an external drive full of data, or install a new application, mds_stores has to index all that new content. Depending on the amount of data, that indexing process can take a while and spike CPU usage during that time.

Major macOS updates – When you upgrade macOS to a new version, Apple often makes changes and optimizations to the way Spotlight works. That means mds_stores usually has to rebuild its index from scratch after an OS update, which can mean higher-than-normal CPU usage for a while, especially on older Macs.

Spotlight re-indexing – Sometimes Spotlight‘s index can become corrupt, incomplete, or out-of-date, causing problems with searches. In those cases, macOS may force a re-index of part or all of your drive, which means more work and higher CPU usage for mds_stores.

Buggy or incompatible software – Occasionally, third-party apps or system add-ons can interfere with the proper functioning of mds_stores and Spotlight. Outdated, buggy, or incompatible software can cause mds_stores to get stuck indexing or use CPU inefficiently.

The good news is that if mds_stores is using too much CPU on your Mac, there are several fairly simple fixes you can try to get things back to normal. Let‘s walk through some steps to diagnose and solve high mds_stores CPU usage.

How to Fix High CPU Usage by mds_stores

1. Restart Your Mac

As with many performance issues, the first and simplest thing to try is restarting your Mac. Restarting clears out temporary files, closes background processes, and gives your computer a fresh start. If mds_stores is stuck indexing or has encountered an error, a restart is often enough to get it back on track. Simply click the Apple menu and choose "Restart".

2. Rebuild the Spotlight Index

If restarting doesn‘t help, the next step is to tell Spotlight to rebuild its index from scratch. This can help if the index has become corrupt or outdated. To rebuild the index:

1. Open System Settings (System Preferences on macOS Ventura and earlier)
2. Click on "Siri & Spotlight"
3. Go to the "Spotlight Privacy" tab
4. Click the "+" button and select your hard drive (usually named "Macintosh HD")
5. Click "Choose" to add it to the privacy list (which temporarily excludes it from indexing)
6. Wait a few seconds, then remove your hard drive from the list by selecting it and clicking "-"

This process essentially turns off Spotlight for your drive, then turns it back on, forcing it to discard the existing index and build a new one from scratch. Be aware that this can take a while, during which searches may be slower than usual and you may notice higher CPU usage by mds_stores. But once the new index is built, things should return to normal.

3. Add Folders to Spotlight‘s Exclusion List

If you have certain large folders that change frequently or contain files you know you‘ll never want to search for, you can improve mds_stores‘ performance by excluding those directories from indexing completely. To do this:

1. Open System Settings (System Preferences on macOS Ventura and earlier)
2. Click on "Siri & Spotlight"
3. Go to the "Spotlight Privacy" tab
4. Click the "+" button
5. Navigate to the folder(s) you want to exclude and click "Choose"

Good candidates for exclusion are folders like Downloads, Dropbox, or external drives containing large photo/video collections, disk images you aren‘t actively using, or developer library/cache folders. Be judicious though – don‘t exclude folders you might actually want to search later.

4. Re-Index Specific Folders

Sometimes mds_stores can get stuck trying to index a particular problematic folder or file. One way to clear that up is to force Spotlight to re-index just that directory. To do that:

1. Open Terminal (in Applications > Utilities)
2. Type the following command and press Enter:
   sudo mdutil -E /path/to/problematic/folder
3. Enter your admin password if prompted

This command deletes the existing Spotlight index for the specified folder and tells mds_stores to rebuild it from scratch. Obviously replace "/path/to/problematic/folder" with the actual path of the folder that‘s giving you trouble.

5. Check for Malware

While macOS is generally pretty resistant to malware, it‘s not entirely immune. Certain types of malicious software can interfere with normal system processes like mds_stores and cause them to behave erratically or use too many resources. If you suspect a virus or other malware may be causing the problem, scan your system with a reputable security program. There are many options available, both from Apple (XProtect and MRT) and third parties like Malwarebytes, Avast, and Norton.

If malware is found, remove it according to the instructions provided by the security software. In addition to potentially fixing mds_stores, this is just a good practice to keep your Mac safe in general.

What If mds_stores CPU Usage Stays High?

If you‘ve tried all of the above steps and mds_stores is still consistently using a lot of CPU, there are a few other things you can check:

Give it time – If you recently added a lot of new files, upgraded macOS, or noticed Spotlight re-indexing, sometimes the best solution is simply to wait. Let your Mac idle for a few hours and see if CPU usage eventually drops back down as the index is built/rebuilt. Remember, some temporary high CPU usage by mds_stores is expected from time to time.

Check Activity Monitor – Open Activity Monitor and select the "CPU" tab. Make sure "%CPU" is showing and look for mds_stores. If it‘s consistently above 50-80% and stays there for a long time, then you may have a bigger problem. As a temporary fix, you can select it and click the "X" button to force quit the process (it will restart on its own).

Disable Spotlight – If all else fails and mds_stores is making your Mac borderline unusable, you can turn off indexing entirely with this Terminal command:
sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist

However, this should only be used as an absolute last resort, as it will completely disable Spotlight search. To re-enable it later, use:
sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist

Contact Apple Support – If none of the above has helped and you‘re still seeing persistent high mds_stores CPU usage, it may be time to contact Apple support or take your machine to an Apple Store or authorized service provider to dig deeper.

Key Takeaways

While high CPU usage by the mds_stores process on your Mac can certainly be frustrating, it‘s usually not difficult to diagnose and fix. Remember these key points:

• mds_stores is part of the Spotlight search engine and is responsible for indexing files on your hard drive
• It‘s normal for mds_stores to use more CPU when indexing lots of new files or after an OS update
• If it‘s causing problems, try restarting, rebuilding the Spotlight index, excluding folders, re-indexing specific directories, and checking for malware
• Some occasional CPU spikes are expected, but consistently high usage may indicate a deeper issue
• As a last resort, you can disable Spotlight indexing entirely, but this will break search functionality

Hopefully this guide has helped you better understand the mds_stores process and how to troubleshoot it when needed. With a bit of patience and these tips, you should be able to get your Mac running smoothly again in no time.