Activity monitor shows process "mdsync" using up all the CPU.

Question

Activity monitor shows process "mdsync" using up all the CPU.

Anyone know what mdsync is, how to control it, and if it has anything to do with the fact that my photo library external SSD refuses to eject even when forced?

MacBook Air (M1, 2020)

Posted on Apr 7, 2023 4:57 PM

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Answer 1

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SaphrynShikaze Author

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20 points

Apr 24, 2023 8:07 PM in response to SaphrynShikaze

Thank you both. I had never had mdsync run at 99% CPU for this extended period of time, which caused the worry.

It turns out Spotlight was reindexing <4TB worth of photos and footage, the same reason it wouldn't let me eject the SSD that said files are on.

Take-aways

"mdsync" is Spotlight, and high CPU usage means it's indexing.
To avoid indexing large SSDs for smoother ejection, go to Settings > Siri & Spotlight > Spotlight Privacy, and add the SSD to the list of locations not to be indexed.

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Answer 2

Apr 8, 2023 6:34 PM in response to SaphrynShikaze

SaphrynShikaze wrote:

Anyone know what mdsync is, how to control it, and if it has anything to do with the fact that my photo library external SSD refuses to eject even when forced?

https://discussions.apple.com/content/attachment/de3cc149-3454-4c94-ab95-92dc6450bf70

mdsync is Spotlight, what happens if you let it run to conclusion as it indexes?

And is there some associated issue...(?)

From the Terminal.app can copy & paste:

diskutil umount

notice the trailing blank space, drag the SSD from the Desktop to the Terminal window to complete the path; use the enter\return key to continue

A SafeBoot How to use safe mode on your Mac - Apple Support will sort many anomalies

ref– see if there is some relief here

mdsync at 99% CPU - Apple Community

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Answer 3

Apr 9, 2023 12:20 AM in response to SaphrynShikaze

When this happens to me it is usually after a safe boot, which deletes the Spotlight index, and resolves itself once it is done indexing.

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Activity monitor shows process "mdsync" using up all the CPU.

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