Hi,
I want to replace my 5400rpm HDD for an SSD without taking it apart or getting to a repairs shop, so would an external SSD do the job?
I would just need to reinstall OS onto the new SSD?
Please could someone elaborate on this?
Thanks.
iMac 21.5" 4K, macOS 10.15
What year model iMac?
Identify your iMac model - Apple Support
If is a 2012 or later, then it has a 5G USB 3.0 bus which gives you plenty of speed to use an external USB 3.0 SSD.
Hello,
While you could use a SSD over USB or Thunderbolt, the data bus is significantly slower than the internal SATA bus. Any speed benefit from the SSD would be neutered by the slow data bus.
It's the 2017 21.5 inch model.
A USB 3.0 SSD could be the way to go.
Cheers.
Yes, that is exactly what I would do. Adding that, I think that you will be amazed at how much faster it runs compared to the 5400rpm HDD.
This applies to all 21.5-inch iMacs with 4K displays: The internal drive bus is 6GBps but Apple insists on install older--and slow-- 3GBps drives in the majority of 21.5 inch iMacs, even some 27-inchers.
You can discover your drive's bus speed with System Information (preloaded). Find and select "SATA/SATA Express" in the left-hand contents pane. You will see something like this if you have the Slow Hard Drive Curse. This from our daughter's iMac 2017 4K 21.5-inch:
Were the drive a fast GBps model, both numbers would be 6.
So if you see that drive spec, your max transfer rate is 3GBps today. An external USB3 enclosure containing a 6GBps SSD will transfer up to 5GBps, as den.thed says. Actual drive performance tests from the EtreCheck utility posted here show measured increases (in MB/s) from the 50-70 range (5400 rpm factory drive) or 90-110 (7200rpm factory drive) up to 400 with the external 6GB SSD. Huge difference and very noticeable in use.
The USB external is a cost effective option. However be certain the external drive is USB3 and the SSD inside is rated 6GB or you will be back to Square One, or worse.
External SSD replacing Internal HDD
