SOLVED External SSD: Ignorant question


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I have a late 2015 iMac that I really like but a couple of months ago I was talking to tech support because Big Sur had crashed the computer and the tech told me my fusion hard drive is failure-prone and had in fact passed its expected lifespan! Apple won't install a new drive so the implication was I had to buy a new computer. Well, that's not happening. So I bought an external SSD (Samsung T7, 1TB). I hooked it up and migrated everything to the new drive. Seemed to work but I have a few admittedly ignorant questions:
  1. Will the computer now use only the external SSD? That's what I want.
  2. Should I erase the internal HD?
  3. I have another external drive: a Seagate 3TB conventional HD that I use for Time Machine backups. Does that "know" to backup from the Samsung SSD or do I need to make some changes?
  4. Am I missing anythin?
Thanks in advance for any and all help here.
 
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I have a late 2015 iMac that I really like but a couple of months ago I was talking to tech support because Big Sur had crashed the computer and the tech told me my fusion hard drive is failure-prone and had in fact passed its expected lifespan! Apple won't install a new drive so the implication was I had to buy a new computer. Well, that's not happening. So I bought an external SSD (Samsung T7, 1TB). I hooked it up and migrated everything to the new drive. Seemed to work but I have a few admittedly ignorant questions:
  1. Will the computer now use only the external SSD? That's what I want.
  2. Should I erase the internal HD?
  3. I have another external drive: a Seagate 3TB conventional HD that I use for Time Machine backups. Does that "know" to backup from the Samsung SSD or do I need to make some changes?
  4. Am I missing anythin?
Thanks in advance for any and all help here.
As long as your external SSD is assigned as your startup drive, and if you reformat the internal drive, your external SSD should stay as your startup drive until you choose another (bootable) volume as startup. If the internal drive is usable after reformatting, you can use it for non-critical storage if you don’t trust its integrity. You can choose whether or not to back up its content to Time Machine.

I did a similar setup for a client and since the internal drive was still working well (the external SSD was solely for speed improvement), we assigned the internal as a second Time Machine drive. Having at least two TM drives, in my experience, is vitally important. After all, data drives, spinner or SSD, cannot be expected to last forever.

I’m not familiar with Thunderbolt 2, which your iMac should have, but if it’s possible to connect the Samsung SSD to Thunderbolt 2, you will be able to gain some speed as well as enable TRIM on the drive. A USB connection cannot use TRIM. TRIM is essential in “optimizing” the SSD. You can enable it using Terminal.
 
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Thanks a lot Tony! Two follow-up questions (no good deed goes unpunished):
  1. Do I need to do anything to "assign" the SSD as the startup?
  2. I may try using the internal drive as a Windows machine. Will have to look into that but it might be fun to play some Windows or DOS games once in a while. I wouldn't care about losing those ;)
Thanks for the Thunderbolt tip. My machine does have it so I'll have to see if the Samsung SSD will work with that. It came with a USB-A cable (which I'm using) and a USB-C cable. Maybe I can buy a TB cable. I did not know about TRIM so will look into that. Thanks, too, about advantage of having 2 TM drives. Never thought of that. I suppose I can set that up in TM?
 
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hmmmm. This is a learning experience. After a frustrating search for adapters I now realize that USB-C and Thunderbolt have the same connector IF it's TB 3. My Mac has two TB 2 ports. Now trying to find a female USB-3/TB-3 to TB-2 adaptor. Not having much luck. Plan B might be to buy a TB-2 cable and a TB-2 to USB-3 adaptor. Or just keep my SSD plugged into the USB A port.
 
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Thanks a lot Tony! Two follow-up questions (no good deed goes unpunished):
  1. Do I need to do anything to "assign" the SSD as the startup?
  2. I may try using the internal drive as a Windows machine. Will have to look into that but it might be fun to play some Windows or DOS games once in a while. I wouldn't care about losing those ;)
Thanks for the Thunderbolt tip. My machine does have it so I'll have to see if the Samsung SSD will work with that. It came with a USB-A cable (which I'm using) and a USB-C cable. Maybe I can buy a TB cable. I did not know about TRIM so will look into that. Thanks, too, about advantage of having 2 TM drives. Never thought of that. I suppose I can set that up in TM?
Yes, I was not sure about Thunderbolt 2 to USB. I made the jump from no Thunderbolt (MacPro5,1) to a Mac mini 2018 which only had Thunderbolt 3/USB-C. Maybe someone here with experience connecting a drive via Thunderbolt 2 could inform us whether a Thunderbolt 2 connected drive shows up as a SATA device in System Information. I have four SSDs connected to my Mac via Thunderbolt 3 that are TRIM enabled. The only time you have to re-enable TRIM is when you reset your PRAM.

Anyway, once you erase the internal drive, and no other bootable drive is connected except for your Samsung SSD, it will default to using it as your startup drive. However, it’s always good practice to assign it anyway (System Preferences -> Startup Drive).

Before you get around to using the internal drive for other purposes, you can try using it as a secondary Time Machine drive.
 
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How did you "migrate" everything to the SSD? To b e able to use it as a start up drive, it would need to be bootable, so it would need to be a Clone of the iMac's internal drive.

Assuming you have a bootable SSD, you can designate it as the start up drive in two ways:
1. Start the iMac on the internal drive, then go into Sys Prefs>Startup Disc, and select the SSD. The iMac should then use that from then on.
2. With the SSD connected, start the iMac while holding down the Alt/Option key. You should then see the two hard dives on the screen. Select the SSD. Again it should the use the SSD from then on.
 
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Thanks again Tony. I do have the SSD assigned in System Preferences. I think I'll leave thie new drive plugged into the USB A jack. There does not seem to be any such thing as a female USB-C to male Thunderbolt 2 adaptor. The only option, as far as I can tell would be to buy a TB2-to-TB2 cable and a TB2-to-USBC adaptor (USB-C goes to the SSD). Kind of Rube Goldberg and rather expensive. And after all that my understanding is there will be no speed improvement.
Regarding using the internal drive for a second TM disk, I went into Time Machine and it shows the Seagate 3TB. Under that is "select disc" but it shows the Available Disks" as Seagate 3TB and ")ther AirPort Time Capsule". If I click "Setup" it shows my AirPort Extreme Base Station so I dunno. Off on a tangent, now I have to find out why the 2 AirPort satellites don't show up. And off on another tangent, I've had to use Time Machine a couple of times. As a former Windows user I'm extremely impressed with how well (and easily) Time Machine works.

MG: Your method sounds easier. I Googled how to make the SSD bootable. Took a little while. IIRC I erased it then chose to format with the correct Mac format. Had some trouble partitioning it but eventually after a lot of Googling got that done. Then it was pretty straightforward to migrate everything to the new "machine" (i.e. Samsung SSD). All seems good now. The 1.02 TB Fusion Drive still shows up but is not called Mac HD anymore. The new SSD shows up with a USB connection, as does the Seagate backup drive.
 
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Thanks again Tony. I do have the SSD assigned in System Preferences. I think I'll leave thie new drive plugged into the USB A jack. There does not seem to be any such thing as a female USB-C to male Thunderbolt 2 adaptor. The only option, as far as I can tell would be to buy a TB2-to-TB2 cable and a TB2-to-USBC adaptor (USB-C goes to the SSD). Kind of Rube Goldberg and rather expensive. And after all that my understanding is there will be no speed improvement.
Regarding using the internal drive for a second TM disk, I went into Time Machine and it shows the Seagate 3TB. Under that is "select disc" but it shows the Available Disks" as Seagate 3TB and ")ther AirPort Time Capsule". If I click "Setup" it shows my AirPort Extreme Base Station so I dunno. Off on a tangent, now I have to find out why the 2 AirPort satellites don't show up. And off on another tangent, I've had to use Time Machine a couple of times. As a former Windows user I'm extremely impressed with how well (and easily) Time Machine works.

MG: Your method sounds easier. I Googled how to make the SSD bootable. Took a little while. IIRC I erased it then chose to format with the correct Mac format. Had some trouble partitioning it but eventually after a lot of Googling got that done. Then it was pretty straightforward to migrate everything to the new "machine" (i.e. Samsung SSD). All seems good now. The 1.02 TB Fusion Drive still shows up but is not called Mac HD anymore. The new SSD shows up with a USB connection, as does the Seagate backup drive.
Does this mean you still haven’t installed macOS on the SSD? A safer way of transitioning to this new drive is to boot into Recovery (cmd-R), select (launch) Disk Utility, from the pull-down on the toolbar (to the left of “Disk Utility,” labeled view) select “Show All Devices.” Assuming you haven’t formatted the SSD yet and it’s blank, select the Samsung device and then click on “Erase.”

Select APFS for the format. Don’t encrypt. Give it a name (e.g. Macintosh SSD). (Do the encryption after installing macOS and then turn on FileVault.)

After this, you can run First Aid, but probably not necessary assuming the SSD is brand new. But it won’t hurt. Run First Aid on the container, and then on the volume. Quit Disk Utility and move on to Install macOS ________ (whatever Recovery decides is the latest version for your Mac).

When the installation is done, it will ask for the source for migration. You can use your present system drive, or latest Time Machine backup. When the migration is done, it will restart and you are all set!

I just finished erasing and installing Monterey on my startup drive myself, just a few minutes ago. I have done this so many times that I’m getting really good at it. Monterey 12.2 RC is not yet working properly, so I used Recovery to downgrade to 12.1 (21C52). I will wait for a stable version of 12.2 before installing it on this machine again.
 
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Does this mean you still haven’t installed macOS on the SSD?
Sorry. Guess I wasn't clear. Some time after my original post, and before your helpful reply, I did indeed install Monterey 12.1 on the external SSD and everything is fine. I did not see APFS, I chose Mac OS Extended (Journaled) as the Format. When I tried to install the OS I got a message saying I had to have a GUID partition but there was no option for that so I googled how to do it. All went smoothly after that.
What I have not been able to figure out is how to have two Time Machine discs.
Thanks again.
 
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Time Machine will view the external Monterey setup as a new computer(I think) so you won't be able to "Enter Time Machine" using your original TM backup. So, you will have to a new TM backup from scratch, and just keep that one.

That was certainly the case when I migrated from my MBP to my new MBA.
 
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Off on a tangent here. I'm a little nervous about reformatting the internal fusion drive but that should be fine, right?
I did try running Boot Camp Assistant, thinking I'd make the internal fusion drive a Windows machine just for fun but the first thing the Boot Camp Assistant says is to disconnect all external hard drives. But one of the external drives is my new Samsung SSD and that's what I boot from. I also have the 3TB Seagate that I use for TM and an old Simple Tech 320GB that I could use (actually I'll probably give the Simple Tech to a friend).
So any advice on how to set up Windows on the doomed internal fusion drive?
Thanks.
 
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I'd say this is a Fool's Errand.
I have a late-2015 27" iMac. When my Fusion drive went last year, I simply took it to a local reputable repair shop and had them install a 1TB SSD to replace the System drive (I always have a very current backup of system drive, using SuperDuper, so it was easy).
Finding a workable TB2 to TB3 adaptor was impossible. USB 3 external drives are way too slow. The new sys drive is faster than the old Fusion drive, and my iMac continues to perform like new.
 
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Hmmm... When I spoke to Apple support and they told me the fusion drive would soon die, and that Apple would not replace it, the rep told me I "could" take it to an independent shop "but" it is extremely difficult to open the case without causing damage so he advised against it. What did I know? Glad you had a good experience. Wish I knew of a good independent Mac repair shop here in northern NJ or southern NY. And yes, I did quickly learn the difference between TB 2 and TB3 and that there's no adaptor.
 

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