M2 Mac mini writing excessively to disk.

Ian R. Brown wrote:

Can anyone explain why I am seeing this massive increase in writes and more importantly how to stop it?

The original external boot drive was Sonoma and the new one is Sequoia.

That is root activity and there is no way to stop it.

The mds_stores and other numbers will always be higher for awhile after upgrading or moving to a new drive.

I haven't restarted in 12 days and I'm seeing this in the Activity Monitor.

If you are worried about using up the Mac mini's internal SSD I wouldn't. Because my 2018 Mac min's internal SSD has been used heavily every day for 6 years and it is no where near reaching end of life do to read/write usage.

First, a whole lot of stuff starts happening when beginning with a new drive and a lot of tasks start running (more than normal) and depending on the amount of RAM that you have there could be memory swapping that could eventually go away. In addition, with starting anew, a lot of items need to be rebuilt and bookkeeping taking place. Note that kernel_task is responsible for memory swapping.

Also note, that Activity Monitor is the sum total of all reads and writes across all mounted drives and stuff can be read and re-written to them as part of macOS filesystem and Spotlight scans. It also resets after every reboot or shutdown and is only totaling use since the last reboot.

Also, check in ~/Library for any very large disk usage. If you have something like Daisy Disk, Omni Disk Sweeper, etc. it can make it easy to sort everything in order of size. Something may have gone ballistic and started writing massive amounts of data to caches or other databases. You may also have encountered a Spotlight going berserk issue that has been seen occasionally (happened to me once).

Something I use to track individual disk is a command line app called smartctl although you can get commercial GUI based apps that can do the same thing like DriveDx. Since the drive is a Thunderbolt drive these can access that info directly without any special USB driver (the USB MSC class has no direct way to read SMART data).

I would suggest getting one of those apps if you did not find any out of line data in ~/Library, establish a base line and then check perhaps daily and see how much the writes change.

"Could you detail the Terminal command please."

After disabling System Integrity Protection,

- to disable Spotlight, type:

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist

- to enable Spotlight, type:

sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist

If this fixes it for you, perhaps file a bug report to Apple.

("I updated it to 15.1.1 and early signs are that the writing has been reduced." But perhaps it is fixed already.)

As @Woodmeister has said, booting from an external drive complicates matters considerably including side effects like degraded performance not to mention wearing out of external drives. None of those issues are reportable to Apple because it is not something Apple recommends (although does officially support setting up).

Separately, Activity Monitor is meant to assist troubleshooting known problems, not find new ones based solely on its or some other 3rd party app’s statistical output. Furthermore, AM’s output is aggregated across all drives and can’t be drilled down further by users.

FWIW, you could try reinstalling on a freshly-formatted external. But IIWY, I’d go back to factory and do away with external boots altogether.

Here’s the good news: I’m outta ideas and (almost) outta here 😁…all the best.

I and others have had this problem, which persists since at least Ventura, although not for everyone, and probably mostly with external drives connected.

The only way to solve it for me was to disable System Integrity Protection after starting up in Safe Mode and then disabling Spotlight via terminal command.

Monitor system RAM usage for swap being used. If you have a system with 8GB of RAM there could be excessive disk swapping taking place and try to find the app(s) that is responsible.

I run off an external Thunderbolt SSD and on a normal day of web browsing and other light tasks I will see about 30-40GB daily with my system with 8GB of RAM. When I do a photo processing session, that can jump to 100-150 GB of writes to disk and sometimes more if I use apps simultaneously or I do particularly complex edits and additional disk swapping takes place. However, I am not too concerned as the 1TB SSD has an endurance of 1665TBW (1.0TB OWC Aura Ultra III). At last measurement, its lifetime is about 59 years at the current usage rate and two years I have used about 4% of its life.

Also, if you do have a bunch of drives, Spotlight will be doing a lot of writing creating its search databases on a new system start up or new boot drive start up.

One last note, because of the speed of SSDs these days, you may not see a huge performance hit, especially if you have moved from a slower drive to a faster drive.

Set it to not sleep first (and leave it that way permanently irrespective).

I would start with disabling Sleep and shutting for long absences and overnights - you know what to do, cheers

Great, your reluctance noted, nevertheless please keep (restart first) and update after a suitable period (i.e. 1 day or more)