Making external SSD drive my primary drive

Well, here is my experience which I hope would be helpful for some of you to make a good decision going forward.

I purchased two years ago a 27" 5K iMac, base configuration. I got it on sale for $200 less, and being new to the iMac world I thought this would be a good entry point to give it a shot.

Don't take me wrong, this is a very, very nice computer, much better than any PC I have ever owned, but I also have to mention that I own a MBP 2015 model with an SSD drive in it, and when I compared the speed between the two is night and day. Boot time on the MBP is way faster, app open time is 2 seconds compared to 14-15 seconds on the iMac (HDD), and at some instances in very demanding situations, it would lag a little. I'm not a computer expert so this was my HARD way of learning the importance and difference of a HDD (even though is 7200 rpm) and a SSD drive.

If you have the budget, always, always, buy a fusion drive or flash drive. If you need additional storage you could buy a reasonable priced external HDD or SSD.

If you don't have the budget, then this is still a very nice computer.

Now, I don't have an iMac with a fusion drive to compare between iMac's, I just compared an iMac between a MBP, but I think the results would be similar, the iMac with the SSD version will be much faster, with the same processor and same RAM as the HDD one.

Here's what I did:

- Purchased a Sandisk extreme 500GB EXTERNAL SSD ($170 @ Best buy or Amazon). This is a 3.0 USB drive.

- Formatted this drive so it can be read and written by the iMac. The instructions are here. How to set up and use an external Mac startup disk - Apple Support

- Loaded OS Sierra to it. The instructions are here. https://support.apple.com/en-us/HT204904

- Then loaded a backup copy of my files and apps from Time Machine.

- Finished.

I ended up with an external SSD with macOS as my bootable drive, and because I restored my information from time machine, everything was there.

Now boot startup speed and app opening speed are incredible. They match even my MBP's.

The overall performance got very much improved. It feels like a high end machine.

I highly recommend the procedure. And it is a low budget one, I only spent $170 dollars and ended up with a 500 GB SSD drive on my iMac, plus the 1TB HDD that I now use for most of the file storage. The apps and files that I need high performance on are on the SSD. Files that I just need to access them sporadically or very small files I store them on the HDD.

I would be hesitant at this point to go to a SSD TB version for improved speeds, taken that most of my work on the iMac is light, and the speeds that I'm seeing right now match my MBP with an internal SSD in it. I think for most of us an SSD through 3.0 will deliver incredible results.

Additional note - I have not read anything about the durability and reliability of an external SSD as a boot drive, so I guess I would need to find out for myself. So far so good. Also, the internal HDD has and keeps the original macOS, so if anything happens to the external drive, I would just simply boot from the internal again.

Hope it helps!

This is a long-running thread, but it will always be evolving due to new hardware, so here is my experience with a decently successful attempt at moving my life onto an SSD for extreme portability:

(1) I purchased a Samsung T3 1TB SSD for a little less than $400 from Amazon (plus a $7.59 BOVKE case for protection).

(2) Using Disk Utility I erased and partitioned the Samsung T3 SSD with a GUID partition map and a single 1TB journaled, encrypted partition. Sometimes Disk Utility gets confused partitioning drives. You may have to physically disconnect and reconnect a drive for it to re-discover the actual state of the drive. This doesn't seem to represent any drive defect, because I have seen it with multiple drives.

(3) Using the latest "Install macOS Sierra.app" from the Mac App Store, I put a fresh copy of macOS Sierra 10.12.5 on the 1TB drive.

(4) Once the Mac did its first reboot from the newly installed OS (this step takes 15 minutes or so), I used a Time Machine backup to restore all of my previous software and settings onto the 1TB drive.

(5) Expect to have to go through a lot of iCloud sign-ins, re-setup Bluetooth devices, etc., simply because not every setting transfers via Time Machine. For example, one such step was a resynchronization of Photos.app with iCloud Photo Library. If you have 2FA, keep your second factor handy.

If you plan to use the external drive to boot multiple machines (e.g., one at home and one at the office), expect to run into random and annoying software licensing issues even if all software you use is on the SSD and is only ever used on one machine at a time. For example, Tableau will complain that there is a problem with "Trusted Storage" in this scenario. Even some software purchased through the Mac App Store is requiring repeated sign-ins (e.g., VOX) as I move back and forth between home and office.

On my early-2015 MacBook Air, the external drive is slower only on very data-intensive applications (like Lightroom scrolling through dozens of photos). Otherwise the machine is just as snappy as it is when booted from its (smaller) internal SSD.

I was having the same "spinning ball" problem with my Late-2013 27" iMac with 8GB RAM and 1TB HDD. The latency when switching applications or user accounts was terrible. I was considering to upgrade to a newer iMac, until I realized that an SDD would fix the issue. I followed a procedure similar to brianrhill's and Armando charger's, but in my case, I tried to make a minimum investment, just to make sure that the SDD approach was the right way to speed up my iMac.

My strategy was to transfer to the SDD just the OS and application files, and keep all user files in the HDD.

My rationale for this was that most I/O slowdown was related to reading system files. I obtained that OS+config+apps+libraries accounted for 65GB in my drive.

Next, I bought a cheap and small 120GB Kingston drive and a USB3 enclosure.

Once I got the drive, I followed these steps:

1. Make a Time Machine backup of my iMac.

2. Format the new SDD drive with a GUID, bootable, single journaled HFS partition.

3. Download El Capitan (the same OS version I have in my iMac) and install it in the SDD.

4. Boot from the newly installed OS in the SDD.

5. Recover my applications and setups from the TM backup. NOTE that I did not transfer user accounts.

6. Boot again from SDD.

7. Manually make a copy of user configuration files from the HDD to the SDD. From Terminal (with root privileges):

USERDIR=/var/db/dslocal/nodes/Default/users

HDD_ROOT="/Volumes/Macintosh HD"

SDD_ROOT="/Volumes/SDD Drive"

cp "$HDD_ROOT/$USERDIR"/[^_]*.plist "$SDD_ROOT/$USERDIR"

8. Replace /Users directory in SDD with a link to the HDD directory. From Terminal (with root privileges):

mv /Users /users.sdd # this folder could be deleted, but I preserved it just in case

ln -s "/Volumes/Macintosh HD/Users" /Users

9. Reboot and enjoy the SDD !!

The resulting configuration works dramatically faster than the older one, at a cost of 71€ (Canary Islands, Spain). Due to the USB interface and the low-cost drive, the actual I/O speedup compared to the HDD is not impressive (8x in reads, may be 2.5x in writes), but the effect in responsiveness is awesome!

Another benefit of this setup is that I still can boot from the HDD, thus I can revert to the old state of things.

My plan is to stay with this setup for a couple of months and then buy a larger SDD (maybe a 500GB Samsung) and have it installed in the internal SATA port as a replacement of the current 1TB HDD.

Replying to myself with an update. I have abandoned this strategy due to three sources of inconvenience:

(1) It's a minor hassle physically to be connecting/carrying an external drive.

(2) My machines are slightly but noticeably less snappy. Keep in mind my machines are early-2015 generation MacBook Airs. This means that they don't have the current-generation USB-C port.

(3) Multiple pieces of software (including iMessage, iCloud, Lightroom, Tableau and Office) are requesting that I repeatedly sign in each time I move between the two MacBook Airs. Sign-ins get old after a while.

It's a bit sad that this strategy isn't quite viable, given that Jobs imagined when NeXT built the NeXTcube that we'd be moving between machines with a 256MB magneto-optical disk cartridge containing the operating system and all your apps and docs.

Yes. Go to the Startup Drive preferences and select the external SSD. I run my system the same way.

I am doing exactly that with my late 2013 27" iMac (though with different SSD).

The SSD is mounted in a Seagate Thunderbolt adapter (commonly known as

"the sled" because of shape). The internal HDD is a backup drive now.

Be sure to repartition the new drive with a GUID partition table (should be default

in options), otherwise it will not be bootable.

Champeau wrote:

Will run the Samsung software so it is recognized.

I could be wrong but I think this step is a mistake. Unless something has changed Disk Utility is all you need to partition and format the drive. Proprietary drive software is usually unnecessary and sometimes problematic.

A 250 Gb SSD is large enough for my OS X and applications and I have everything else on the stock HDD. I used this article when I set up my internal SSD/HDD iMac http://mattgemmell.com/using-os-x-with-an-ssd-plus-hdd-setup/

This is pretty much exactly what I'm about to do - already boot from an SSD via thunderbolt but I've just got a couple of 480G Intel SSDs in a Startech dual drive TB enclosure and another enclosure with a 1T Samsung 850 for backing up.

I'm hoping it'll all work as planned, TRIM enabled or not I'll be guided by those with more knowledge, but it seems a shame to waste the existing capacity on the internal HDD.

At the risk of sounding stupid, can I use the HDD for time machine backup if almost everything else is run externally? Bit back to front I know, thought it worth an ask. Just to be extra stupid is it possible to configure RAID on just the dual drive? I suspect it is as the other drives have different names and identities.., but I'll be pleased to be proved wrong.

Most grateful for anyone's advice, even if it involves terminal commands... I can copy and paste...

Thanks in advance.

http://pondini.org/TM/21.html and this http://pondini.org/TM/2.html

The late Pondini will have just about every answer you're looking for regarding Time Machine.

if almost everything else is run externally?

In addition to Pondini's suggestions, be careful with the "almost everything else is run externally". It is best not to mix Time machine and other files/copies/whatever on the same partition. If you want to keep some stuff on the internal, partition it: one for the "stuff" and one for Time Machine.

Thank you so much for the help and info, both of you, what a mine of information.

How has this worked out for you? I was thinking of doing the same thing with the newer Samsung T3, but then I read that USB drives like this don't support TRIM. I don't know much about this stuff, but apparently TRIM is particularly important for boot drives.

Thanks.

I have an SSD from OWC (macsales.com) and they claim theirs do not need it as the garbage collection is taken care of - I do not have enough knowledge on that subject to say anything other than what they told me. But you might want to check with them.

Thanks for your reply. Which SSD did you buy and are you using it externally as a boot drive?

Ok, so you plan on using an external SSD your primary boot disk? I had this same questions too about a month ago with my 21" iMac. Unfortunately, because it happens to be external, USB or Thunderbolt connections bottleneck the speed performance of the OS to the rest of the computer, which is inside. The internal HDD, which is connected via SATA, has a faster experience due to the connection type. Now if you were to install it internally, it wouldn't even be a close comparison. I did many hours of research between other responses, different threads scattered on the internet as well as testing it on my own Mac.

Can my iMac boot from an external disk?

Here's the link to the post that I had. You should be able to find useful information in there with the links I remember posting in one of the replies. All in all, it's your choice, and it wouldn't hurt to try since you already purchased the SSD.