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Oct 24, 2018
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I upgraded my Mac Mini 2018 (is set up as a server but with a normal OS and hardwired into the network) to OS 15.2 from OS 14 and since than SSD and Other Hard Disks attached to it (Via USB) are very slow to access from the network. And I mean slow. This is compared to previously. Any idea as to why this should be so? Fixes?
 
I upgraded my Mac Mini 2018 (is set up as a server but with a normal OS and hardwired into the network) to OS 15.2 from OS 14 and since than SSD and Other Hard Disks attached to it (Via USB) are very slow to access from the network. And I mean slow. This is compared to previously. Any idea as to why this should be so? Fixes?

Are you by chance using Encrypted APFS?
 
On the Hard Disk is indeed an encrypted disk image that I use. and yes all SSD are encrypted.
Why do you ask? As they worked fine like this under OS14.
 
On the Hard Disk is indeed an encrypted disk image that I use. and yes all SSD are encrypted.
Why do you ask? As they worked fine like this under OS14.

Agree the upgrade shouldn't have slowed down your I/O but reports of slowdown with external drives -- especially encrypted -- under Sequoia are growing:



 
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Thanks for the links. does anybody know if this has been reported to Apple?
 
I have 2 External SSD for the iMac M3 24gb 8/10 core. Both of them starts fast then slows down then speeds up again then slows down to a crawl. I transferred 300gb of data to each one. One at a time to test. It starts off super fast...then about 1/4 or 1/2 way it starts the fast/slow/fast/slow/ action... so this is caused by Mac OS 15.2? Using OWC Thunderbolt 4 cables.
 
I have 2 External SSD for the iMac M3 24gb 8/10 core. Both of them starts fast then slows down then speeds up again then slows down to a crawl. I transferred 300gb of data to each one. One at a time to test. It starts off super fast...then about 1/4 or 1/2 way it starts the fast/slow/fast/slow/ action... so this is caused by Mac OS 15.2? Using OWC Thunderbolt 4 cables.

Did this just start recently (e.g. with upgrade to macOS 15/15.2) or has it been like that since you got the machine/these SSD? What make and model of external SSD?

Which filesystem (APFS, HFS+, exFAT) are you using on these SSD? Are they APFS (Encrypted)?

How full are your drives?

Note that it is normal (expected even if not ideal) for modern consumer SSD to go fast for the first the ~ 50GB and then slow down dramatically after that. Scroll down to "Sustained Write Performance and Cache Recovery": on this page:

As such when I look for an SSD, I specifically search for those with high sustained performance (after prioritizing high TBW and low peak power draw) rather than peak performance. For external TB3/etc drives, performance above 3GB/sec is inaccessibly anyway so I don't care about that. But thermal throttling, non-cached slowdown, and especially drive failure will slow me down.

In any case, if your issue didn't start with macOS 15/15.2 and/or you aren't using APFS (Encrypted) it is probably unrelated to this thread and probably belongs in another thread. If you do repost in another thread still include the above information as well as your actual performance (e.g. it transfers the first ~ 25% in 25 seconds but then the remaining 75% takes 5 minutes and/or include results from one of the test programs listed in the links to other articles).
 
Note that it is normal (expected even if not ideal) for modern consumer SSD to go fast for the first the ~ 50GB and then slow down dramatically after that. Scroll down to "Sustained Write Performance and Cache Recovery": on this page:
OH..thanks for the link. APFS encrypted on both. I thinks thats what's happening. These drives are 2TB each. 1.73TB Free and 1.54TB free... I'll read up on this first.
 
Thnaks good info. No it started happening after upgrading and they are not full at all. I TB T7 they are. Never had this problem on previous OS'.
 
OH..thanks for the link. APFS encrypted on both. I thinks thats what's happening. These drives are 2TB each. 1.73TB Free and 1.54TB free... I'll read up on this first.

If you are running APFS encrypted it would be great if you could post some numbers for comparison with others. Also which macOS and make and model of enclosure.

If you are running macOS, my guess (speculating without answer to other questions) is that you are hitting both issues -- your drives are going slow due to slowdown of APFS Encrypted in macOS 15/15.2 and then going even slower once you exceed your drives' cache.
 
Thnaks good info. No it started happening after upgrading and they are not full at all. I TB T7 they are. Never had this problem on previous OS'.

Agree the issue you posted about is unrelated to the SSD cache "issue" (known design limitation, etc) and almost certainly a Sequoia 15/15.2 issue with APFS Encrypted. If 'kagharaht' wasn't using APFS Encrypted I would have recommended pursuing in a seperate thread as the underlying causes would have likely been different. On the flip side, now we have another data point from which we can look for commonalities.
 
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