macOS userfsd/spotlight constantly reading external SSD up to 2TB per day

I can't tell whether it's userfsd or Spotlight's fault. It just keeps reading my external SSD at about 10–15 MB/s nonstop after I plug it in, even though I'm not using anything on the SSD. Sometimes it can read as much as 2 TB per day, and I have no idea what exactly 'userfsd' is.

Maybe it's doing something, but 2 TERABYTES PER DAY?? I don't think that's normal for an indexing process.




[Edited by Moderator]

Mac mini (M4)

Posted on Oct 9, 2025 1:30 PM

Reply
Question marked as Top-ranking reply

Posted on Oct 10, 2025 8:45 AM

Xiao_Gan_US wrote:

I formatted it as exFAT.

That's what I thought. Do you really, absolutely have a need for this to be exFAT?


A couple of years ago, Apple had an experimental project to move drivers for non-native formats to user space. The first proof of concept was implemented for exFAT. So what you're seeing in that "userfsd" is activity from the "user file system daemon".


But as Apple typically does with these projects, they dropped it after making it about 60% functional. It does kinda work, as you can confirm. It just doesn't work that well. Maybe they'll fix it next year, or the year after. More likely, they would just re-write it again. Most likely is that they'll simply do nothing.


I recommend reformatting that drive to APFS. If you need cross-platform access, use SMB file sharing. There is very little chance for any improvement. And if there is any improvement, the timeframe will be measured in years.

3 replies
Question marked as Top-ranking reply

Oct 10, 2025 8:45 AM in response to Xiao_Gan_US

Xiao_Gan_US wrote:

I formatted it as exFAT.

That's what I thought. Do you really, absolutely have a need for this to be exFAT?


A couple of years ago, Apple had an experimental project to move drivers for non-native formats to user space. The first proof of concept was implemented for exFAT. So what you're seeing in that "userfsd" is activity from the "user file system daemon".


But as Apple typically does with these projects, they dropped it after making it about 60% functional. It does kinda work, as you can confirm. It just doesn't work that well. Maybe they'll fix it next year, or the year after. More likely, they would just re-write it again. Most likely is that they'll simply do nothing.


I recommend reformatting that drive to APFS. If you need cross-platform access, use SMB file sharing. There is very little chance for any improvement. And if there is any improvement, the timeframe will be measured in years.

macOS userfsd/spotlight constantly reading external SSD up to 2TB per day

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