Making external SSD drive my primary drive

This was for my mid 2012 MBP and I got the Mercury Electra 3G (due to the cost at the time; the 6G was beyond my budget). In any case, I installed in the MBP replacing the slow 5400 rpm stock drive. I don't know that having an SSD as an external boot drive is all that beneficial unless you have a superfast connection. I've been happy with that drive since I installed it in 2012.

It is night and day: boot time is about 15 seconds from switch-on, including log-in screen, apps open instantly, backups go unnoticed, everything just faster and smoother. I don't use the computer for anything serious like video editing but it gets put through its paces time to time, and it's not far off my MBA for performance - that's newer with i7 and PCLe flash.

There are fixes I've read about moving libraries and files to the boot drive, yet this seems to have happened without me doing anything which is weird, all the new stuff goes there and iTunes etc. seems to have migrated, maybe I did something with a disk image when booted internally? Whatever, everything points there now and I use the HDD as nothing more than a backup for an earlier OS.

One thing I will say is that there are no bottlenecks with thunderbolt, it's ridiculously fast and, of course, supports TRIM (not available via USB) which keeps everything tidy. I'm a little suspicious about garbage collection, reckon the mac will do what's best and do hard drives really have that much autonomy? The SSD connection in the enclosure is SATA anyway, probably slower than what thunderbolt can handle.

As I said though, for a three year-old computer it's given it a new lease of life, well worth the money for me because although replacing the internal HDD with SSD might just edge it on speed (and definitely on cost, I wouldn't take an iMac apart!) there's a lot of flexibility and choice for additional storage. I mean 1TB, 2TB, more? 20 seconds to swap drives in the Startech, there's a lot to like.

"All in all, it's your choice, and it wouldn't hurt to try since you already purchased the SSD."

I haven't actually purchased the SSD, or even the computer yet. I'd like to get the 27" iMac, but I'm on a tight budget and looking at the base model with the 1TB HDD, probably a refurb. I'm pretty sure it would suit my needs at the moment, but I know I'll want to upgrade the boot drive to SSD in the future. Since Apple makes upgrades so difficult, a small external SSD like the Samsung T3 seemed like a very easy and cost effective way to upgrade. These drives will probably get bigger, faster, and cheaper by the time I'm ready to upgrade too. So that also seemed like a bonus, but I don't want to regret not getting an internal SSD if external ones are going to be problematic. Thunderbolt drives and enclosures seem too expensive, and the read/write speeds seem similar to USB, so I don't think I'd go that route.

I was responding to Champeau.

I wouldn't use an external drive over an internal drive, even if it is thunderbolt. Buy the time that you purchase the external drive, and possibly an enclosure for it, you'll be around the same price as an iMac with an internal SSD. I'd just wait, save up a little more, and get the Mac with the whole package. If you're going to spend this amount, be sure it's for what you want. I know brand new it's an extra $200, but then you'd receive the fusion drive. I see refurbished, it would run you an extra $170 for the fusion drive, which still makes it $100 cheaper than a brand new version of the regular HDD iMac.

Thanks for the feedback. I bit the bullet and ordered a refurb today with a 256SSD and 16GB RAM. It was $440CAD more than a base model refurb with the HDD and 8GB RAM, but only $90 more than a brand new base model. It was still more than I wanted to spend right now, but with the SSD and the extra RAM hopefully I won't be worrying about any upgrades for awhile.

Cheers.

Hi.... any issues having the SSD recognized as the boot drive with El Capitan?

Nope. That is what I do. Just select it in the Startup Disk preferences.

I have imac 1tb 27" (1yr old, new thin shape); it is quite slow. Also have MBP with internal SSD which is super fast. Thinking of buying external T3 as an extra bootable drive (to permit compatibility of software which doesnt like Sierra!)... how is yours running, if you now have it all up and running?