Slow and fluctuating transfer speeds in Finder on High Sierra iMac Pro

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Level 1

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Slow and fluctuating transfer speeds in Finder on High Sierra iMac Pro

Hi, I was wondering if anyone has experienced anything similar.

I bought my iMac pro back in June, and I’ve been experiencing weirdness regarding finder transfer speeds.

I work in data management in the film industry, and while copy / paste-ing let’s say about 700 gb between my fast RAID setup (1.200mb/s read speed, Thunderbolt 3) and an external hard drive (USB3 drive, 180mb/s write speed), the finder will tell me that it will take about an hour to copy these 700gb worth of files.

But then 40 minutes later it’ll say 8 hours or so (or just seemingly stopped copying all together). Unless I start working on the mac again (move the mouse etc) then the speed picks up again (sometimes even this doesn't work, sometimes it just stays slow)

BUT, if I use the Terminal application to perform these transfers, this slowdown doesn't happen. Which is making me think it's the operating system's fault.

Is this a High Sierra issue, or is this an iMac Pro issue?

iMac Pro, macOS High Sierra (10.13.6)

Posted on Nov 29, 2018 2:50 AM

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Answer 1

a brody

Level 10

85,314 points

Dec 2, 2018 8:04 AM in response to benjo2709

Neither. Actually all data transfer is done in serial, so it is a series of pulses to represent whole packets being transferred. When one file is being transferred, it is subject to any multitasking happening while the transfer takes place. http://www.bombich.com Carbon Copy Cloner allows you to copy whole folders or individual files from place to place with much more reliability than the Finder. This is especially true for large data transfers. Part of the problem is in the Finder's overhead from Spotlight that wants to index everything, and possible issues with data integrity. And if you are transferring multiple files, the rate of transfer will vary for each file because the effort to maintain the integrity varies by file. Disabling Spotlight helps, disabling Time Machine helps, and making sure there are no other memory resident antivirus programs or data sharing programs.

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Slow and fluctuating transfer speeds in Finder on High Sierra iMac Pro

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