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iMac with fusion drive and ssd

R

Rubberman

macrumors newbie
Original poster
Oct 30, 2017
21
1
I have a late 2013 iMac with the 128gb fusion and the 1tb mechanical drive. I installed a 500 gb SSD in place of the OEM 1tb drive and added 16gb of ram. Blackmagic is showing its now slower than it was with the old mechanical drive. Can you not have both the SSD and Fusion drive together?

I have the PNY CS900 which is Sata 3.
 
To my knowledge the 1tb fusion drive did not have a 128gb ssd. Did you break the fusion drive before installing the SSD? Are you now running as two separate SSDs? Blackmagic on the fusion will only show SSD speed and not likely to use the spinning drive. Have you run it on the two drives separately?
 
The older 1TB FD came with 128GB SSD I believe.

OP, do you want to split the drives or use them as one drive which is like a fusion drive but both drives are SSDs in your case.

How to split up a Fusion Drive

Whether you made your own Fusion Drive and want to go back, or want to split up one you got from Apple, we'll show you that it isn't a difficult or lengthy process.
www.macworld.com www.macworld.com
 
glenthompson said:
You are correct, the first fusion used a 128gb drive, then they dropped it to 24gb, then upped it to 32.
Click to expand...

Wow did they dropped it to 24GB before, that’s terrible... 32GB is bad enough IMO. At least the new iMacs are all SSDs now, finally!

I just bought a second hand iMac 2019 with 1TB FD, will be interesting as I have never used a FD before...
 
henry72 said:
The older 1TB FD came with 128GB SSD I believe.

OP, do you want to split the drives or use them as one drive which is like a fusion drive but both drives are SSDs in your case.

How to split up a Fusion Drive

Whether you made your own Fusion Drive and want to go back, or want to split up one you got from Apple, we'll show you that it isn't a difficult or lengthy process.
www.macworld.com www.macworld.com
Click to expand...

I want it to run faster then it did it OEM. So which ever method - splitting or making them 1 drive - is better .
 
OP wrote:
"I have a late 2013 iMac with the 128gb fusion and the 1tb mechanical drive"

No, you DO NOT have (had) that.

What you had was a:
- 128gb SSD blade
and
- 1tb platter-based HDD.

The "fusion" is "in the software" (drivers), that "melded" the two separate drives together to "appear as one" on the desktop.

It's possible that the fusion drive (or, perhaps just the SSD portion of it) was running faster than the 2.5" SATA SSD that you installed to replace the HDD (the SATA SSD maxes out around 500-525MBps, I reckon).

What you need to do is this:
1. Download the free "Blackmagic Speed Test" (I think it's in the Apple Store)
2. Test your newly-installed SSD
3. Test the original 128gb SSD
4. Post BOTH RESULTS here so we can see them.
 
I used black Magic before I swapped the mechanical 1tb HDD then used again after the SSD replacement. The write speeds were similar. The read speeds for the SSD were way slower
 
Haven’t done anything with BlackMagic on a fusion drive so this is conjecture. When you ran the test on the fusion drive it’s likely that all the activity was to/from the SSD blade. That interface may be much faster than the SATA interface to the spinning (now SSD). The SSD in the fusion serves as a cache, holding the most used items from the other drive. If you did split the fusion when installing the SSD then that would account for the speed disparity. Do you have two drives visible in the iMac? If so then the fusion is split and you should run BlackMagic on each drive. Not sure if it’s needed on your machine but do you have trim enabled?
 
Rubberman said:
I used black Magic before I swapped the mechanical 1tb HDD then used again after the SSD replacement. The write speeds were similar. The read speeds for the SSD were way slower
Click to expand...

Did you reinstall macOS after installing the SSD? If not, FD could be corrupted? https://support.apple.com/en-gb/HT207584

I don't think you can just swap the drive because macOS manages the data.

Please remember backup your data...
 
Here are some results with BlackMagic (16gb ram installed)

Original 1TB fusion drive
Write------Read
1. 281 ------ 560
2. 265 ------ 593
3. 256 ------ 604

PNY SSD installed
1. 357 ------- 358
2. 208 ------- 257
3. 166 ------- 223

PNY SDD installed in USB3.0 enclosure and booted
1. 255 ------- 310
2. 160 ------- 310
3. 160 -------309

PNY wants me to send it in
 
I suggest you try another SSD -other than- PNY.
Try Crucial or Sandisk.

This time, get an EXTERNAL 2.5" SATA enclosure, like this one:
tinyurl.com

SABRENT 2.5 Inch SATA to USB 3.0 Tool Free External Hard Drive Enclosure [Optimized for SSD, Support UASP SATA III] Black (EC-UASP)

SABRENT 2.5 Inch SATA to USB 3.0 Tool Free External Hard Drive Enclosure [Optimized for SSD, Support UASP SATA III] Black (EC-UASP)
tinyurl.com

Put the SSD into it and connect it to a USB3 port.
Do this, and you will get reads in the 420-430MBps range.

Is the original SSD portion of the fusion drive still in place inside?

Your BEST option:
DO NOT USE FUSION ANY MORE.
Instead, "split" the fusion drive into separate drives (you probably already have done this by removing the HDD).
Now, use the internal Apple SSD as a 128gb boot drive.
It will run fastest this way.

Use the other drive for "large libraries" of stuff, such as movies, music, and pictures.
 
The speeds were faster because BlackMagic only writes/reads a few Gigabytes that fit completely on the internal SSD, even the 24GB or the 32GB version of later 1TB Fusion Drives. Thus, when running the benchmark before you were really benchmarking the SSD portion of your Fusion Drive, which is faster than your new SSD, and not the much slower HDD portion, which is much slower than your new SSD.

If you want the best of both worlds you can recreate the Fusion Drive and have that same experience as before, only faster because it won't slow down as much as soon as it has to revert to the slower high-capacity portion of the Fusion Drive.
 
How do I recreate the fusion drive ?
For ***** and giggles i have a SP ssd and reinstalled macOS on it to see and it’s the same speed.
 
Google it. There are millions of guides and how-tos around.

FYI, another option would be to install macOS and all your applications on the fast 128GB SSD and use your SATA SSD as additional storage for user data.
 
Here is a post from Apple support regarding fixing a split fusion drive (that's essentially what you have). fix split fusion

Let us know what happens/has happened with the benchmarking after re-creating the fusion drive.
 
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