How can I install Mac OS onto a new ssd? iMac

While USB drives have their place for data storage they are not overly fast even a SSD drive. This gets into speed of the USB interface of your system yours is only a USB 2.0 (480 Mb/s) Vs the faster USB 3.0 (640 Mb/s) then you have the older FireWire 800 interface which offers (800 Mb/s) theoretical throughput. The last external interface your system has is a Thunderbolt (first generation) port which offers 10 Gbps of thoughtput.

So now let’s use a model which is a better way of looking at this. Think of water which is under the pressure which pipe will off more water using the throughput numbers I just gave you as their diameter. Of course the Thunderbolt is the biggest and the USB 2.0 is the least.

Now while I’ve been discussing throughput we also need to think about that other element the water pressure in our model. If we have the same pressure across all of the interfaces there are conditions which the water (data flow) won’t offer much difference. This gets down to the ability of the storage medium to either send the data or accept it. A slow HDD won’t offer much more than what a USB 2.0 can offer so that’s not that good. A slow SSD (thumb flash drive) is around what a USB 3.0 can offer. Newer SSHD and SSD’s are able to leverage what the FireWire and Thunderbolt interface can offer. We can even gain more performance by ganging up multiple drives together which is called RAID’ing.

OK, a lot to consider!

So what do I recommend? I would make the effort to open the system and add in your SATA III (3.0 Gb/s) SSD as the best investment. I would leave the slower HDD in the system if it’s still running. While a bit more work it will offer the best bang for the buck. Here’s the guide you’ll need to follow Installing iMac Intel 21.5" EMC 2428 Dual Drive Kit and the needed parts iMac Intel 21.5" (Mid 2011) Dual Hard Drive Kit plus your own 2.5” SSD.

So why is this the best option? First using the SSD as your boot drive and hosting your apps only you don’t need as big a SSD ($$). If you replace your HDD for the SSD you will also need to install a special thermal sensor adapter and need a much larger SSD. Here’s the needed kit: iMac Intel 21.5" and 27" (Mid 2011) SSD Upgrade Kit and the guide: iMac Intel 21.5" EMC 2428 Hard Drive Replacement. As you now you’ll want your content also on it. Where the dual drive config we can leave your data on the HDD.

OK, I really don’t want to open my system can I just go with an external drive? Yes! Either a FireWire or Thunderbolt Gen 1 external SSD drive will offer good performance. To max it out I would get a RAID’d external drive. Now the other shoe drops… Finding these older drives is getting harder! As both FireWire and Gen 1 & Gen 2 Thunderbolt drives have been replaced by a still faster interface Thunderbolt Gen 3 using USB-C!