@flowrider you're absolutely right that blind flight support could cause the OP more trouble than he had before and it can never be as effective as a well educated guess with all necessary info. I'm glad that you asked for the details.
But hey, where's the fun?
In
another thread the OP is mentioning a 2012 MBP with a Samsung EVO 840.
TL;DR - However, just considering this post:
The OP is talking about a 2012 Mac with a SATA cable. MacBook is out, cause not produced in 2012. MacBook Air and rMBP 2012 10,1 or 10,2 are out as they do have a flash drive with no SATA cable. Hence, it's a MacBook Pro 9,1 or 9,2 non-retina, a Mac Pro 5,1 (desktop or server) or a Mac mini 6,1 (desktop) or 6,2 (server). Correct me, if I'm wrong! Concerning the slow drive speed does the exact model really matter? Maybe, if you bring in the cache that is different though these models. But in fact it was faster before the APFS conversion and more slowly afterwards. Very unlikely that the cache suddenly changed or got broken during upgrade.
The SSD connection type must be 6.0 Gbps Serial ATA (SATA) or in case of a Mac Pro a 3.0 Gbps Serial ATA (SATA) controller, no matter if attached to an optical drive connector or a hard drive interface. Again, IMHO it doesn't matter so much as there was a speed degradation after file system conversion. Very strange that it's the 5th cable, but who knows what's going wrong there?
If I don't misread, the OP has TRIM support enabled, but just didn't look at the right place. That problem is solved.
The one really important question is, what the exact SSD model is, as there might be some known issues with a specific model. E.g. the EVO 840 has
reported speed degradation over time. The linked article is just referring to read speed, not write speed. Then the next question arises, what firmware is on the drive and is there a better one available?
Updating a disk drive with newer firmware is fine, but IMO it's something one should think about twice. New firmware, especially for Samsung SSDs, very often is introducing new bugs that haven't been there before. This happened to me with an EVO 850. Samsung unfortunately has no dedicated firmware update tool for Mac and it's a bit of pain to deal with their .iso installers or attaching the SSD to a Windows machine that can't read it without reformatting. Nevertheless, the model and installed firmware version could help to narrow down the problem and give a more educated advice. I don't recommend upgrading to the latest firmware, except it's known to address the write speed degradation of that certain model in question.
Until the OP is telling us the missing facts, IMHO there is nothing wrong with a little blind guessing. I don't see any advice here that will potentially harm the OP's Mac or drive, do you? To defend myself, e.g. in my last post, I tried to exclude the possibility that there are too many unconsidered apps writing to the drive.
As it's not a professional helpline here, we should all be interested in learning by helping and asking. I hope that the OP returns with some answers and won't be aggrieved by some comments here, like I felt a bit so that I had to ask myself if I should really write or finally post another comment. I hope you don't mind.
