Help with Ext SSD iMac

[glynnwaterworth]

Hi,
I have an iMac with the Fusion Hard Drive, which since installing Big Sur is now running slower.
Would an external SSD possibly a Thunderbolt one speed the Mac up ?.
I have tried an old SSD connected by USB and this seems to work ok but wondered if a new thunderbolt device would be much better.

Many thanks,
Glynn

 

[Fishrrman]

How about telling us which year iMac you have?

In most cases, a USB3 SSD will help. It gives read speeds of 430MBps.

If you have USBc ports, you could put together an "nvme" blade SSD and a USB3.1 gen2 enclosure, and get read speeds of 800MBps.

If you have thunderbolt 3 connectivity, you could buy a tbolt3 SSD. These yield very fast reads, around 2,000MBps, but they're expensive and they can "run on the hot side"...

 

[glynnwaterworth]

Hi
Thanks for your advice
The imac specs are
3.4Ghz quad core intel core i5
8 GB 2400 Mhz DDR4
Thunderbolt /USB4

look forward to your reply.

 

[Fishrrman]

To my knowledge, iMacs don't have USB4 yet.
It would have USB3 (I would think).
The tbolt3/USBc ports support USB3.1 gen2.

See my first reply above.
Pick the speed you want, and the price you're willing to pay.
That's about it.

 

[MacCheetah3]

The imac specs are
3.4Ghz quad core intel core i5
8 GB 2400 Mhz DDR4

Based on that, I'm concluding a 2017 iMac @Fishrrman

have an iMac with the Fusion Hard Drive, which since installing Big Sur is now running slower.

Apple did get APFS (Apple File System) to eventually work with Fusion, but the two indeed do not play well together. I say that with experience. Also, unfortunately, for us Fusion drive users, APFS is required for macOS Catalina and Big Sur. Therefore, best to either move away from Fusion or not upgrade OS. With that said, an external is certainly an option if you want to avoid the time/cost of upgrading the internal.

I have tried an old SSD connected by USB and this seems to work ok but wondered if a new thunderbolt device would be much better.

When you say USB, I assume, you mean one of the USB type A ports, correct? If so, those ports allow up to about 400MB/s of throughput in real world performance. Maybe your "old" SSD can't provide that, maybe it can. Even if it can, let's move on. You can go Thunderbolt 3 with a mid to high-end SSD and have it achieve as much as 3,000 MB/s. Although, the price tag matches so to speak. The third external alternative is USB 3.1, for example:

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You'd connect the drive to one of the iMac's Thunderbolt ports (USB-C). Even though it uses the traditional USB protocol rather than TB, USB 3.1 gen. 2 can attain up to about 900MB/s in real world performance, which is not bad.

Basically, unless you need/want top-notch storage performance and finances aren't an issue, I'd suggest a newer USB 3.1 (10Gb/s) drive if you want to go with an external-type storage upgrade.

 

[glynnwaterworth]

Thanks for that.
So in comparison what write speed id
s the Fusion Drive ?

 

[MacCheetah3]

Yours could be faster than mine as Apple's Fusion is PCI-E SSD + SATA HDD and mine is an aftermarket with both the SSD and HDD connected via SATA.

Anyway.... Just now....

Techtool Pro 13 reported:

~36 MB/s write
~140 MB/s read

Blackmagic Disk Speed Test:

~7 to 13 MB/s write
~175 to 252 MB/s read

As you can see, in both, the write speed is notably crippled.

During average tasks, Web surfing, etc, I really didn't notice. Nevertheless, I decided to go with a USB 3.1 SSD (limited to USB 3.0) and have reads and writes ~400 MB/s.

 

[glynnwaterworth]

An Update.
I bought a Crucial X8 1TB SSD USBC
The machine is transformed, so thank you for all the advice. It runs really fast now.

Is there a way of making it back up to the original internal drive ?, either through Time Machine or otherwise ?.

Thanks again.

 

[Fishrrman]

OP:

What size is your internal drive?
1tb, or something else?

Since you are booting and running from the external SSD, you could use the internal drive "as your backup".
However...
I recommend that you use CarbonCopyCloner to "clone" the contents of the boot SSD to the internal, so the internal will remain "a bootable drive" as well.

WHY you should consider doing this:
What happens if something goes wrong with the external SSD?
How will you boot the Mac?
If the internal is a bootable clone, you just boot right up (even if it runs slower).

 

[MacorNothing]

Hi ! I think connecting via thunderbolt is better than usb main quick writing. For example, few months ago I was buy a SSD X5 Samsung, connecting in Ext, on TB3. It's better now.
Have a good day (I hope that my English will be understand)