I succeeded to boot once and the computer was working great. Then I reboot again after trying to update , it failed to reboot. It seems like it completely not recognizing the external ssd, although if I unplug and plug it back, it would recognize it in disk utility, but not recognizing as start up disk. Any thought?
iMac 21.5", macOS 10.13
It turns out that it might have been USB cable. After I tried everything everyone has suggested, I have re installed the system numerous time, I decided to switch the cable between a sandisk extreme ssd which I used as a back up and the Samsung t5( which I have the Mac OS on), and it has been workinglh flawlessly since.
It turns out that it might have been USB cable. After I tried everything everyone has suggested, I have re installed the system numerous time, I decided to switch the cable between a sandisk extreme ssd which I used as a back up and the Samsung t5( which I have the Mac OS on), and it has been workinglh flawlessly since.
I am not sure what version of macOS you are running on the T5 or the internal drive. Try holding down the Shift key on restart. Keep holding it down until the drive icons appear on the screen. See if your T5 now shows up. If it does select it and restart. Older versions of macOS do not see the newer APFS formatted drives in the startup disk window.
I noticed that I mistakenly said to hold down the Shift key on restart. That is wrong. I should have said, hold down the Option key on restart until the drive icons appear. Sorry for the mistake.
I have a 1TB Samsung T5 (external USB powered SSD) running macOS Mojave and it works just fine. The T5 does have to be reformatted though, as it comes formatted as ExFat with Master Boot Record partition scheme. The T5 needs to be erased and reformatted APFS with a GUID Partition Map before installing macOS Mojave.
Please carefully read the instructions in https://support.apple.com/en-us/HT201314 , if you removed the drive that was already in the computer or it's totally dead then start where discuses If you can't start up from macOS Recovery so you can do an Internet Recovery. The external drive MUST be formatted first and have a GUID partition. It you cannot execute this then take the computer to your local Apple Authorized Service Provider who can do the work correctly.
I am using a T5 as a boot drive right now. Power is not a problem. The T5 uses 896ma of the 900ma that is available, with no extra current required. The T5 is hooked up to a USB 3.0 port. I checked and the 2012 iMacs have four USB 3.0 ports.
I would think that the USB ports on your particular iMac don't provide enough power to the POWER HUNGRY T5.
I guess I was just assuming that you were running Mojave. What version of macOS are you running on your system?
thanks everyone for your advice. I had successfully erased , partitioned and reloaded the Mac OS on the Samsung t5 ssd , it was working fine till it prompted me to update, after I downloaded the new Mac OS , at that point the computer still recognized the t5, the computer asked me to restart the computer. And the Mac fails to reboot or recognize the Samsung t5 to reboot after. I made sure I had the Samsung t5 set at the startup disk before I restarted the computer. It just would not recognize or reboot from it even if I pressed the option key at the start up. It gives me a white blank screen for a few mins, then the apple logo would show up. Then it goes to a black screen and back to apple logo again then it would bring me back to the disk utility screen . I don’t u derstand why it doesn’t start from the external Samsung t5 after the update.
Yes, I ran through the whole process, and I was able to do everything that I normally do. But same as the last time as soon as I downloaded the new update of the Mac OS and q nap app( external storage for Mac) and tried to restart to install, even though I selected the t5 as the start up disk, when I actually restarted the computer, it would get no where. Blank white screen....then apple logo with a bar that would only went half way then black screen ....then greyish offwhite screen with apple logo again...then a screen that asks me to select language...then the recovery screen again. If I pressed the option key when I power on, the recovery drive rather than the t5 would show up before apple logo, when I choose it same process would happen. And the blue light on the t5 is completely solid, instead of blinking the whole time. I was able to boot and function before the 2 update( Mac OS and q nap) . Not it is as if the Mac is not picking up the t5. The night is not blinking at all, just solid. I tried cmd,opt,p,r. Nothing works. Any help would be appreciated.
High Sierra, but it prompted me to update as soon as the computer was function. Not sure if the update or the Qnap app is the problem. But I unadorned the qnap app on the Mac before the computer died, it was fine. Would that be how I downloaded it to the t5?
I have never heard of Qnap. That could be the problem. You could try to uninstall Qnap according to the developers instructions and see if that solves the problem. I have two T5s and and never had any problem booting macOS High Sierra or Mojave from them.
Usually if you start having problems after you install something, it is a good place to start troubleshooting. Do you have a Time Machine backup from prior to the installation of Qnap. If so restart in macOS Recovery and restore from your Time Machine backup.
No, I did not remove anything. Just an external ssd. And I did successfully get it going, just fail to reboot after I shut it down again.
I am not sure I am clear. Were you able to actually boot the T5 as your startup disk before the update? Did you allow the update that was downloaded to go through the whole installation process? It can take 30-45 minutes or more for an update to be installed. It will go through two installation black screens with an Apple logo. Each stage can take 20 minutes or more. After the Apple logo, maybe a couple of minutes each time, you will see a loading bar with a time estimate for installation completion in each phase.
When you use Disk Utility, make sure to have it set to "View/ Show All Devices", so you can set the Scheme to GUID Partition Map. Disk Utility by default is set to "View /Show Only Volumes". This needs to be changed to "Show All Devices" to properly format your T5. Choose the "Samsung Portable SSD T5 Media" in the Disk Utility sidebar and choose "Erase" at the top then choose, Format: APFS and Scheme: GUID Partition Map click on "Erase" at bottom right.
"View" is in the upper left hand corner of the Disk Utility window. Make sure the Partition map is GUID not Master Boot Record.
Attempt to restart in the Recovery Partition (Command + R on boot up) and then open Disk Utility and format the SSD. After it has been formatted correctly then exit DU and install Mac OS on the SSD. Once that is done, if done correctly then restart again this time holding down Option + Command and select the SSD and it should boot up. If this is done incorrectly then you need to take the computer and your SSD to an Apple Authorized Service Provider to have them do the work.
By the way, what brand SSD did you purchase and what brand enclosure are you using, if you purchased a Samsung SSD then you may be in for trouble. Most experienced users on these forums only use OWC (www.macsales.com) SSDs because they work with no problems out of the box.
My vintage 2012 iMac have a drive issue and fail to boot from Samsung T5 external
