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ashleykaryl 07-29-2020 05:52 PM

CPU temperature during backup
I imagine this is all deemed safe and within tolerances but I've been surprised at how hot the CPU becomes on my new mini during backups with SuperDuper. On the old Mac Pro it sits at around 50C, whereas the mini generally hovers between 95-100C.

Looking at the CPU usage in iStat menu it appears to be making full use of the single core and no doubt turbo boost, so I hear the fans racing for a good part of the copy process and the case becomes quite hot. I almost wish there was a way in SuperDuper to turn down the CPU usage and just take a few more minutes over the copy process.

At time of writing I am copying 500 gigs of data from an SSD to an external USB 3 drive while I work and the mini is hovering around 50C, so I am guessing it's the smart update feature that is more demanding of the CPU and pushing temperatures up.

dnanian 07-29-2020 05:57 PM

We're really not terribly CPU intensive except when doing a Time Machine backup, so that's certainly curious. But there's no way for us to "turn down our CPU use" - that's up to the OS, which is what's doing the scheduling.

ashleykaryl 07-29-2020 06:13 PM

It surprised me as well and I wondered if using an SSD for backup effectively releases the brakes, allowing the CPU to race up like that. Time Machine is backing up to a separate drive that isn't SSD and it's not having any major impact on CPU temperature.

dnanian 07-29-2020 07:21 PM

It certainly lets us copy faster, since we're less I/O bound, which would mean over a given time period, we'd be waiting for I/O to complete less, and doing attribute comparisons more.

Plus, note that if you haven't added the backup drive to the Spotlight preference pane's Privacy tab, Spotlight/mds will be doing a bunch of CPU intensive stuff too.

ashleykaryl 07-30-2020 12:15 PM

I added the SSD SuperDuper backup to the spotlight privacy section as you suggested and it still hit 100C but perhaps the temperature stayed 2-3C lower on average over longer periods. That's an impression rather than a scientific evaluation though.

The curious part was when I tried SuperDuper on two non SSD external drives and the temperature there barely rose above 50C when copying 100 gigs of changes earlier, so much like the old Mac Pro.

The high CPU temperatures occur when copying the OS from the built in NVME drive to an external SSD over a 10 Gb/s connection. Apple seem to be fairly relaxed about the high CPU temperatures on the i7 mini, so hopefully it is all within tolerance.

dnanian 07-30-2020 12:40 PM

It specifically limits itself when it hits thermal maximums, so there's really nothing to worry about.

SuperDuper doesn't treat SSDs any differently than any other drive: as I said, it's likely that it's just able to do its job faster.

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