Fusion Drive and Slow Performance?

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Level 1

90 points

Fusion Drive and Slow Performance?

The last few days I have been posting on some discussions about slow performance and using OS Sonoma. After some recommendations by a member of the community, I think I found out what the problem has been all along. I think this problem has been with me for a very long time as I have not been very happy with the performance of my iMac over the last year or so. I have my old iMac from 2012 and it was running circles around this one.

There are a lot of posts out there about Slow Performance with Sonoma and I followed everyone's advice on remedies such as START UP IN SAFE MODE, RUN DISK FIRST AID, ETC. with no results.

My operating OS was something that I cannot mention here and I received some criticism for that. THAT WAS NOT THE PROBLEM!!!!

My next step was to erase my hard drive and reinstall Sonoma. When I did that there were mysterious drives, showing up such as untitled and so on. After I recovered all of my data from a Time Machine back up everything was the same, slow as a turtle.

My next step was to install Sonoma on an external SSD and recover all my data from the same time machine back up. When I restarted finally, after all of the things I had to do, I was totally amazed at the speed. This Mac is now running at light speed. Everything is just instantaneous. When I open Safari, it just jumps out on the screen to the homepage. When I open mail, the mail just jumps out at me. While doing these tasks, the computer is backing up to Time Machine, and it is not restricting any speed at all. Which used to almost stop any actions.

Using the internal Fusion Drive my read and write speeds were:

Write speed: 54 MB/s

Read speed: 77 MB/s

Using the External SSD my speeds are:

Write speed: 801 MB/s

Read speed: 908 MB/s

QUITE A DIFFERENCE, RIGHT

I hope I did this correctly and this post stays up and helps others as I think the root of the problem was the internal fusion drive on this Mac. I am attaching and EtreCheck report which will list the specifications of my iMac.

Gary's iMac (2) 2024-04-07 W EXT DRIVE

iMac (2017 – 2020)

Posted on Apr 7, 2024 08:32 PM

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Answer 1

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Gary Davison Author

Level 1

90 points

Apr 12, 2024 08:18 PM in response to BDAqua

As a follow up on my situation, I have more information to pass along to anyone that has an iMac with a Fusion Drive.

I hope this post does not get taken down. So, please read and copy as it may.

Since my last report, April 7, 2024, concerning Fusion Drive and Slow Performance, describing the use of an external SSD I have taken some more steps to determine the problem. I was not willing to give up on the internal hard drive. I took my iMac to an Apple Store and had some diagnostics run on it. The built in diagnostic test and a more advanced diagnostic test run by the apple Genius showed no problem with my internal drives.

I started all over again and wiped my Macintosh HD and reinstalled Sonoma. I restored my files from a Time Machine backup. Still I had terrible performance. Also, two Macintosh HDs were showing up on the desktop. One was 1TB the other was 28GB. The 28GB had no files on it. I contacted Apple Support again and inquired as to why there were two drives showing up. The advisor that I was connected to, failed to understand that there should not be two Mac HDs showing up.

Last evening, I again contacted Apple Support and I lucked out and was connected to a very knowledgable support person. He walked me through and emailed me several procedures to troubleshoot the problem. Following all of his direction, I wiped and reinstalled again but did not restore my info from the Time Machine backup and I did not connect to my iCloud Drive. Still the same results, 2 Macintosh HD on the desktop and very slow.

Alas, I contacted Apple Support again and was connected with another very knowledgeable support person. After reviewing the previous contact info from the previous rep, she contacted the upper level support (I think). FINALLY, THERE WAS SOME INTEREST THAT MY FUSION DRIVE HAD SPLIT!!!!!!!!

I was given the option of shipping my iMac into Apple for inspection or trying a procedure to "FIX A SPLIT FUSION DRIVE". I followed the procedure and BINGO!, I am back to one Macintosh HD and all seems very good. Using the built-in Fusion Drive, my READ SPEED is now 1476 MB/s and the WRITE SPEED is 774 MB/s. Below I will list a link to the instructions to restore a SPLIT FUSION DRIVE.

I know this has been a very long post but I hope it helps everyone that is experiencing slow performance on a Mac with a FUSION DRIVE.

I am especially grateful to the last two support agents that helped me. Sometimes you may get connected to a support person that just does not understand that you may know what you are talking about and will not contact upper tier support.

This is the link to the instruction to "HOW TO FIX A SPLIT FUSION DRIVE".

How to fix a split Fusion Drive - Apple Support

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Answer 2

BDAqua

Level 10

250,007 points

Apr 8, 2024 07:01 AM in response to peterpatter

Hi Peter,

Sadly you cannot use either the 2017 iMac or newr Minis for traditional Target Screen mode...

The following older iMac models can be used as an external display when plugged into another older Mac model.

iMac models introduced in 2011, 2012, 2013, and mid 2014

To use any of these iMac models as an external display:

The iMac used as a display must have macOS High Sierra or earlier installed.
The other Mac that you're connecting it to must have been introduced in 2019 or earlier and have macOS Catalina or earlier installed.
The cable connecting the two Mac computers must be a Thunderbolt or Thunderbolt 2 cable.

24-inch and 27-inch iMac models introduced in 2009 and 2010

To use any of these iMac models as an external display:

The iMac used as a display must have macOS High Sierra or earlier installed.
The other Mac that you're connecting it to must have been introduced in 2019 or earlier and have macOS Catalina or earlier installed.
The cable connecting the two Mac computers must be a Mini DisplayPort cable.

Use your iMac as a display with target display mode - Apple Support

Note: Target Display Mode isn’t supported on iMac models with Retina display. Only iMac (27-inch, Late 2009), iMac (27-inch, Mid 2010), and iMac (Mid 2011 to Mid 2014) support Target Display Mode. Target iMac also must be running 10.13.6 or less.

I haven't tried either, but Turn any Mac or iPad into a second display...

https://lunadisplay.com/

Review by NAK005, you may not be happy with it…

Secondary Screen Solution - Apple Community

https://www.duetdisplay.com/

Duet - Remote Desktop, Second Display, Drawing Tablet, and More (duetdisplay.com)

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Answer 3

BDAqua

Level 10

250,007 points

Apr 7, 2024 10:01 PM in response to Gary Davison

Nice work, Fusion drive was a bad move on Apple's part.

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Answer 4

Old Toad

Level 10

214,272 points

Apr 13, 2024 12:11 PM in response to peterpatter

You can't use the iMac's 27" screen as a monitor for a new Mac Mini. It's not supported. The monitor Mac must be 2015 vintage or earlier and the using Mac must be vintage 2019 or earlier.

You can get 32" LG monitors w/speakers for about $300 or 27" monitors w/speakers from $110 to $200.

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Answer 5

Apr 8, 2024 12:51 AM in response to Gary Davison

Thanks Gary,

I also have the slowness problem with my fusion drive Drive iMac (Retina 5K, 27-inch, 2017) purchased in 2018 with 1TB of storage and only 8GB of RAM, which is sufficient for my needs. I've been thinking of purchasing a Mac Mini and using that in conjunction with the excellent 27-inch screen. My OS is Ventura 13.6.6. I am at present holding off upgrading to Sonoma. Can I replace the Fusion Drive with an internal SSD and then only use an external drive for storage?

Thanks, Peter.

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