Slow SanDisk SSD

[JohnBoy5562]

I have a 2015 iMac and want to speed it up for editing photo. i installed a SanDisk 2tb SSD and installed the latest OS. But my iMac was faster when it had a fusion drive. After I installed the SanDisk SSD my iMac is running slower than it was with the fuSimon drive. What do I need to do to make the SanDisk run as fast as the apple SSD from the fusion drive?

 

[ptfuzi]

You need to get a sabrent and the adapter and install in the same slot as the apple ssd

 

[JohnBoy5562]

You need to get a sabrent and the adapter and install in the same slot as the apple ssd

 

[JohnBoy5562]

I put a SSD in my 2011 iMac with out any problem. And it was a 5 times increase in speed. The only difference is this iMac had a fusion drive.

all I did was taken the fusion drive out and replaced it with a SSD. I did use A thermal control adapter.
but as you can the SSD I replaced make my iMac run slower.

 

[JohnBoy5562]

The SSD I bought.

 

[JohnBoy5562]

how can I make a fusion drive like before? This SSD has slowed down my iMa.

 

[Fishrrman]

Hmmm....

Are you saying you took out the HDD portion of the fusion drive, and installed a 2.5" SATA SSD in its place?

A 2.5" SATA SSD is not going to be as fast as the "blade SSD" that comes as the SSD portion of the fusion drive in the iMac.

THAT'S WHY when you test the blade separately (looking at the images above), it "tests faster" -- because it IS a faster SSD.

As ptfuzi said, if you want speed to [roughly] equal that of the blade SSD (of the original fusion drive), then you have to replace the blade SSD with an "nvme" blade SSD AND the appropriate adapter.

You wrote in reply 4:
"I put a SSD in my 2011 iMac with out any problem. And it was a 5 times increase in speed. The only difference is this iMac had a fusion drive."

Of course it was faster in that case, because you replaced a platter-based SATA drive with a SATA SSD.

But "the rules are different" with the 2015 iMac and the internal fusion drive.

On the 2015 iMac, you've replaced the [slower] HDD portion of the drive with an SSD.
The SSD is faster than the HDD, yes, but -- nowhere near as fast as the factory-installed blade SSD.

OK, so where does this leave you?
My advice:
Leave things as they are right now.
DO NOT "re-fuse" the fusion drive.

Instead, make the 128gb Apple blade SSD your "boot drive". It should have the OS, your applications, and "basic" home folder.
Let the 2tb Sandisk SSD become your "second, data drive".
Keep your large data libraries on THIS drive.

If you do this, you will have:
a. a FAST boot drive
and
b. a LARGE, and modestly speedy, data drive.

My opinion only.
It's probably not worth putting more $$$ into a 7-year-old iMac...

 

[DeltaMac]

The OEM SSD is a PCIe card, mounted on the logic board.
Your new SSD replaced the hard drive, and uses the same SATA connection as the hard drive, so you are restricted to the speed of the SATA bus. the 415 MBps is probably around the max, which might hit as much as 425 MBps with the right SSD, but not more than that. Still significantly faster than the spinning drive that you replaced, but still on the SATA bus, and limited to that. The OTHER drive, the original SSD, is on the PCIe bus, which is capable of many times faster speed.
So, if you want faster, you need a device on the PCIe bus. You already have one, the original SSD. But, that is only 128GB - so not a lot of space. It's also an Apple device, using a proprietary connector, so you would need to purchase a used Apple SSD, which are a bit pricey (and would be pulled from another Mac, so used...)
Or, much cheaper to buy a standard PCIe m.2 card, and connect that through one of the adapters that are pretty easy to find -- such as: https://smile.amazon.com/gp/product/B07FYY3H5F.
The MAIN obstacle to doing this - the SSD is mounted on the back side of the logic board, and remvoing that is a challenge, but there are good videos, or step-by-step instructions on iFixit, for example. Not a difficult task, just one where you need to be careful. I just did one like yours a couple of weeks ago, and works greate.
Yes, your iMac is getting some age, but can still be upgraded to current Monterey, maybe the next macOS version, too.

 

[BrianBaughn]

There's a lot in the above posts to unscramble. Simply put, install macOS on the 128GB SSD. From there, you can use the new, 2TB to store your data.

Some folders insist or prefer to reside in your user folder or subfolders of your user folder, storing lots of data there. Learn how to put a "symbolic link" of such a folder to point to the actual data stored on the second drive.

 

[JohnBoy5562]

So I need to start over and put Mac OS on the 128 drive. i Know that I can make my photos Library be on the 2tb SSD. But wouldn’t it be better to refuse to drive and just have one show up?

my problem is editing photos. when using luminar 4 I have to sit and wait on the ball to stop spinning. I want the new M1 Mac but can’t afford it right now.

so which should I do? Refuse the two drives and make a fusion drive. Or just put the os on the 128 app drive.

I thought maybe I should have replaced the 2 sticks of 4GB ram with 2 sticks of 8GB of ram. For a total of 32BB of ram.

editing photos right now is a nightmare.

 

[DeltaMac]

I think it could be useful to watch your Activity Monitor, when your computer appears to slow down. You might find out that it's not memory, and not the SSD at all, but some other issue in your software that is pulling the whole system down.

 

[ptfuzi]

Well you can create fusion drive with both ssd"s, you just need to enter Recovery to run a command in terminal and It will delete everything.

 

[ptfuzi]

Also you didn't need that temperature sensor and that can add a failure point