What portable SSD to use as boot drive?

If you have any of the Seagate utilities installed in the system,

remove them per Seagate instructions immediately. The vendor

supplied crapware will only mess things up and most often

fight against what macOS is trying to do. Seagate stuff i

probably one of the worse offenders. Also, if you have them,

uninstall any antivirus, cleanup apps, "speed up" utilities, etc.

as you don't need them and again they only fight what macOS is

trying to do on its own.

While the suggestions given are good, I have used 1 TB SanDisk 3D SSD

in one of the better quality aluminum StarTech USB 3 enclosures

and it worked quite well. I have since installed it internally and in general use noticed

not much difference than when external. Transfers were on the

order of 350-400 MB/sec with large files. Remember, USB 3 on a

2013 iMac will only be 5Mbit/second rated and is less in practical use. So,

in even in the "ideal world" simple math says the fastest you can ever possibly

get 625 MB/sec and never will happen in the real world.

One thing to note though, it does share USB bandwidth with any other USB

devices that are attached. So if there are any data hungry devices attached,

that will slow things a bit.

This is about the best out there, https://eshop.macsales.com/item/OWC/ME6CM6EPT01/ . The only thing it needs is an external power supply, when ordering ensure you get that added to the order, it should be under $10. There are cheaper solutions out there but if you want reliability, service (pre and post sales) and a vendor that specializes in Mac solutions then my recommendation is the OWC solution.

kennethfromfortbragg wrote:

......And, you say that the most I can get is 625MB/sec (or do you mean 6.25MB/sec?) ....

625 "Mega"Bytes/sec or 625,000,000 bytes per second.

USB3 is very capable as a boot drive with an SSD.

As a comparison, the internal Hard Drive in your iMac

on a "good day" will max out at around 100-110 MegaBytes/sec.

Typically, the external portable hard drives (the small ones), which are usually

only 5400 RPM drives, will max out at 70-80 Megabytes/sec regardless

of what interface is used.

I second rkaufmann87’s recommendation.

While other USB 3.0 SSDs and roll your own USB 3.0 Enclosure/SSD combinations work, that one is better suited and reliable for sustained useage.

If you're not worried about aesthetics this one works well for me:

It's cheaper than a "packaged" SSD and you can easily swap bare SSDs to change boot drives if desired. Also it doesn't need a separate power supply. The SSD is about $160 at OWC (MacSales.com).

Thunderbolt. It's faster than USB but check the speed of the SSD. Unless its faster than USB, Thunderbolt won't help.