Slow write and read speeds on 21.5 2017 iMac 1TB Fusion 8gb 3.4ghz

[Chris Walker]

This is my first iMac and it seems very slow. I did the Disk Speed test.

I tried the Drive DX software trial and that said the Drive was all good.

Any ideas

 

[Loa]

Is it new-to-you?

Is the drive empty?

 

[tyc0746]

What type of drive is in it?

If it's a HDD-only model, then that's about the speed you'll get.

If it's a Fusion model (HDD+SSD) then I'd expect 10 times that (not sure when the SSD went from SATA to PCIe).

If it's an SSD-only model, then you'd expect at least 10 times that (newer machines have faster access to give about 2500mbps).

 

[Chris Walker]

Is it new-to-you?

Is the drive empty?

Yes. Its almost empty.

and yes i just got it. Bought it used.

 

[Chris Walker]

What type of drive is in it?

If it's a HDD-only model, then that's about the speed you'll get.

If it's a Fusion model (HDD+SSD) then I'd expect 10 times that (not sure when the SSD went from SATA to PCIe).

If it's an SSD-only model, then you'd expect at least 10 times that (newer machines have faster access to give about 2500mbps).

I am pretty sure its the Fusion drive as it looks like its in 2 parts. One is about 30GB and the other 1TB.

What type of drive is in it?

If it's a HDD-only model, then that's about the speed you'll get.

If it's a Fusion model (HDD+SSD) then I'd expect 10 times that (not sure when the SSD went from SATA to PCIe).

If it's an SSD-only model, then you'd expect at least 10 times that (newer machines have faster access to give about 2500mbps).

 

[nambuccaheadsau]

That is the problem with a 1TB Fusion Drive ~ only a 32G B SSD which will not hold half of the average operating system. The best solution may be a faster SSD connected externally to USB3, or Thunderbolt and selected as the boot drive.

 

[Chris Walker]

Woulkd something like this be suitable?
Samsung Portable SSD T5 500GB, USB 3.1 (Gen 2) Type-C, Up to 540MB/s,

 

[370zulu]

From the screenshots, it appears that your Fusion Drive has been split. It should show as "Fusion Drive" if it is joined. My 1TB Fusion drive is averaging 600-800 in BlackMagic.

Which macOS version is installed?

Here is an Apple KB article to look at on how to reset the Fusion Drive to default.
*** These steps in this article permanently delete all data stored on the drives that make up your Fusion Drive. ***
*** Make sure that you have a backup before continuing.***

Use Terminal to create a Fusion Drive again

 

[Chris Walker]

From the screenshots, it appears that your Fusion Drive has been split. It should show as "Fusion Drive" if it is joined. My 1TB Fusion drive is averaging 600-800 in BlackMagic.

View attachment 924447

Which macOS version is installed?

Here is an Apple KB article to look at on how to reset the Fusion Drive to default.
*** These steps in this article permanently delete all data stored on the drives that make up your Fusion Drive. ***
*** Make sure that you have a backup before continuing.***

Use Terminal to create a Fusion Drive again

Thanks for the info. Catalina. I have nothing on the machine yet. Would I need to re-load a copy of Catalina if I did the above?

 

[370zulu]

Thanks for the info. Catalina. I have nothing on the machine yet. Would I need to re-load a copy of Catalina if I did the above?

Welcome. Yes, you will have to reload the operating system because it will create a single new drive that you will format during the installation.

 

[Chris Walker]

Welcome. Yes, you will have to reload the operating system because it will create a single new drive that you will format during the installation.

Welcome. Yes, you will have to reload the operating system because it will create a single new drive that you will format during the installation.

Here are 3 screen shots from Disk Utility. I will pop out to get an SSD to back everything up today and then try your suggestion.

 

[370zulu]

Here are 3 screen shots from Disk Utility. I will pop out to get an SSD to back everything up today and then try your suggestion.

From those screenshots it looks like it is definitely split.

Good precaution to take for the backup beforehand.

 

[rbart]

I am pretty sure its the Fusion drive as it looks like its in 2 parts. One is about 30GB and the other 1TB.

Your Fusion drive is disabled (split drives), that's why you hav slow speed.
You have to rebuild it.
Look here:

How to fix a split Fusion Drive - Apple Support

If your Fusion Drive appears as two drives instead of one in the Finder, it's no longer working as a Fusion Drive. Here's how to fix it.

support.apple.com

 

[Chris Walker]

When I go to erase my and format my SSD these are the format options I get. Which one should I chose? My current drive is APFS. Catalina

 

[370zulu]

MacOS Extended (Journaled) is fine.

 

[Chris Walker]

Wow. Fixing the split disk worked a treat look at this screenshot. 8 x faster read and 15 x faster write. I am very happy now. Only about 5 x faster for read and write booting from the SSD. So I will stick with the Fusion for now.

 

[370zulu]

Looks like mine does. Good deal! Enjoy!