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MrTk

macrumors newbie
Original poster
Dec 10, 2013
24
1
Folks:

My sister has a 2015 iMac. Runs the lovely fusion. Well, the SSD appears to have failed. Rather than open it up and risk other issues, I thought about getting her back on her feet by using an external SSD running USB 3.0. This iMac obviously supports 3.0 and Thunderbolt 2.

Option 1: I considered just a WD Easystore 5TB portable drive. Then I started to consider that maybe such a drive wouldn't support throughput that 3.0 can take and I've heard such externals don't support TRIM.

So I am now considering Config 2:

Buying a Hannord (or equivalent) 2.5" Hard Drive Enclosure USB 3.0 to SATA III case. Most such cases says they support SSD & HDD (SATA III) up to 4TB. I would make sure it fully supports USAP too. Match a case with a Samsung 870 QVO Seriese 2.5" 1TB SATA III V-NAND. Both should let me enable TRIM support via UASP.

The question is, would this second option be much faster than the first? It will be more expensive; I just wonder if the performance would be noticeable. With TRIM support via UASP I believe it should have longer life. That's a plus. Just don't know if this will even make a dent in speed differences between the two.

BTW, in another form I read, "USB3 has brought a new protocol : UASP (USB Attached SCSI Protocol) for communication with external mass storage devices over USB. The old protocol BOT (Bulk Only Transport) does not support TRIM. UASP supporting TRIM and NCQ". Option 2 should give me UASP." That is what moved me to consider option 2.

Thoughts?

TKH
 
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WD Easystore 5TB is a HDD (spinning disk), not an SSD.
Samsung 870 QVO has QLC NAND, less durable than 870 EVO (TLC NAND)

I would just buy a 5-year-warranty 1TB 870 EVO SATA, pair it with any cheap USB 3.0 box and give it a go. 500MB/S is fully enough for normal use.
 
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Buy an SSD "for price", not speed. The best speeds you're going to see from USB3 are about 430MBps. That's it (but still pretty good). So again, buy for price.

Just about any 2.5" SATA SSD will do. I like Crucial and Sandisk.

There are many "cheapie" USB3 enclosures out there.
If you want one that's built like a tank (costs a little more), look here:

There are things you haven't told us:
- What size the fusion drive is
- What OS your sister is using
- Whether it was backed up or not

With USB, you're not going to get TRIM support.
Don't bother worrying about it.
There's really nothing more to say on this subject.

Can the iMac boot to INTERNET recovery?
This is NOT THE SAME as "the recovery partition".
Try:
Command-OPTION-R
at boot.

With internet recovery, you can:
- boot the iMac
- get the SSD formatted
- get an OS installed
and
...get running again.
 
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Fishrrman:​


Ok. I have more details.

- Mac is the Late 2015 with 2TB. The iMac 17,1. That means it has 128 DB SSD and the 2TB HDD.
- She is running Big Sur
- She has a Time Machine backup. But doesn't know how current. I know she has it as of at least a few months ago. Thus I do NOT want to touch/reformat the 2TB HDD. I would rather get an external SSD booting OR replace the internal SSD and then check out what the 2TB looks like.

Running Internet Recovery, then jumping into Disk utility she shows these (see attached). That would tell me her iMac can see the 2TB drive...but I don't see a 128GB SSD in there.

Also I assume the OS X Base System is on the 2TB drive. Right? I've never understood where that is stored. If it was stored on the SSD, then it's functioning. I'm a bit confused.

Either way, I think the best step is either:

1) Open up and replace SSD.
2) Don't open, simply add an external SSD (Crucial MX500 2TB drive). Format that and recover her time machine to that drive and boot from that going forward......maybe I should just do a fresh install into that drive then migrate after. Either way, it should boot to USB 3.0 and run fine.....Right?
IMG_6382.jpg
IMG_6381.jpg
 
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"2) Don't open, simply add an external SSD (Crucial MX500 2TB drive). Format that and recover her time machine to that drive and boot from that going forward......maybe I should just do a fresh install into that drive then migrate after. Either way, it should boot to USB 3.0 and run fine.....Right?"

This is my recommendation.

Get the external SSD assembled.

Attach it to the iMac.

Boot to internet recovery.

Open disk utility.

IMPORTANT IMPORTANT IMPORTANT
Go to the "view" menu and choose "show ALL devices".

Now format the SSD to APFS with GUID partition format.

Quit du and open the OS installer. See if it will install Big Sur for you.

Once the clean copy of bs is on it, connect the TM backup.

Now start clicking through setup assistant, and migrate the backup to the SSD.

I'm afraid she'll have to live with "as good a backup" as was the last time she had the tm drive attached...
 
The good news is her backup was current, as of 8/19. So NOTHING lost. Whew.

So I have the system up and running but I've noticed a few issues:

Facts:
A) The internal HDD, I formatted and have it mounted as an internal storage drive. I can write to it fine.
B) When I restarted the iMac, I have noticed a BIG inconsistency in boot times. My best is:
- 21 Seconds till apple appears (I assume this is cause the Mac is searching for the boot drive). Yes, I did make the External Drive (USB) the boot drive in the System Preference/Boot Disk option
- 40 seconds form apple to login screen. Not bad...but not internal SSD speed, of course

I ran speed tests on my two functioning drives:

- SSD External (USB) - 353MB/s Write 355MB/s
- Internal HDD - 160.4 MB/s 201 MB/s

C) Just did another reboot. Went normally quick (Letter B above) but this time the 121GB SSD showed up. I tried to mount it and format it, it didn't play well and froze Disk Utility. Clearly that chip set needs to come out. I wish I could disable reading from that SATA area from bios.

My questions are:

1) Why, when I unmount the HDD it boots with it mounted? I want to remove any likelihood the system is looking to book off of anything other than my external SSD.

2) Is there some other more concrete method to tell the bios that the internal SSD and internal HDD are no longer there?

I sincerely wonder if that is why my boot speeds vary and sometimes it just hangs.
 
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I have a 2019 iMac that I boot from a Thunderbolt 3 connected Samsung X5. instead of the 1TB Fusion drive which I am not using at the moment. I also get the same senario. However itis not a problem as I normally don’t turn the machine off, just put it to sleep. When I wake it up the drive never gets re-mounted. On the odd occasion I reboot the machine I just unmount it again.

Furthermore I also have a 2011 iMac which I boot from a Thunderbolt 1 Lacie enclosure containing a Samsung EVO 860 SSD. The internal drive I wiped and made it a Time Machine drive for backup.
 
OP wrote:
"this time the 121GB SSD showed up. I tried to mount it and format it, it didn't play well and froze Disk Utility. Clearly that chip set needs to come out."

You could try and format it again.
Or even try formatting it to MS DOS.

The goal: have the SSD "formatted, but empty and not used".
So long as it disturbs nothing else, just "let it be" and work around it.

If the internal HDD is fine, just keep using it for extra storage or even as an "internal backup" of the boot (external) SSD.

I'm wondering if the delay during boot was the OS trying to "repair" the malfunctioning internal SSD?
After which ... after "an attempt"... is just "gives up" and looks to whatever else is bootable and available?

I've never tried this myself, but I've heard there are terminal commands that will tell the Mac to "ignore" an internal drive after bootup... that is, to "not mount" it.

For this to work, however, I assume the drive itself must be formatted and "otherwise normal". In your case, the SSD isn't behaving so these conditions aren't met.

If the internal SSD won't format to a "Mac format", I'd try whatever other options disk utility offers, to see if it will format to "ANY format".
This doesn't mean it will become a "usable drive".
But once formatted, again, it can just exist as "empty, left alone".
 
OP wrote:
"this time the 121GB SSD showed up. I tried to mount it and format it, it didn't play well and froze Disk Utility. Clearly that chip set needs to come out."

You could try and format it again.
Or even try formatting it to MS DOS.

The goal: have the SSD "formatted, but empty and not used".
So long as it disturbs nothing else, just "let it be" and work around it.

If the internal HDD is fine, just keep using it for extra storage or even as an "internal backup" of the boot (external) SSD.

I'm wondering if the delay during boot was the OS trying to "repair" the malfunctioning internal SSD?
After which ... after "an attempt"... is just "gives up" and looks to whatever else is bootable and available?

I've never tried this myself, but I've heard there are terminal commands that will tell the Mac to "ignore" an internal drive after bootup... that is, to "not mount" it.

For this to work, however, I assume the drive itself must be formatted and "otherwise normal". In your case, the SSD isn't behaving so these conditions aren't met.

If the internal SSD won't format to a "Mac format", I'd try whatever other options disk utility offers, to see if it will format to "ANY format".
This doesn't mean it will become a "usable drive".
But once formatted, again, it can just exist as "empty, left alone".
I like your thought process, Fishrman, and appreciate the brainstorm.

The latest is the drive stopped showing up, once again. Even when it did, I couldn't format it; it will be read from but not written.

I've seen some postings that suggest in Terminal you enter instructions to remove the SSD from the boot sequence. Sadly, I was unable to get them to work--likely because I didn't fully comprehend what they were doing. I'll have to do some more digging.
 
OP wrote:
"The latest is the drive stopped showing up, once again. Even when it did, I couldn't format it; it will be read from but not written."

I recall reading that some SSDs will "fail" this way -- that is, they'll "fail to" to a "read only" state and can no longer be written to.

The SSDs that I've had fail (all were 2.5" SATA drives) just "went dark" -- never to be seen again.
 
I was able to successfully remove it from being booted via commands in Terminal. Now if I could somehow entire TRIM was enabled on the external USB drive. I've heard mixed things about that actually working.
 
If you could get a used Lacie rugged Thunderbolt drive ( the orange one with the attached thunderbolt cable). Remove the HDD and replace with your SDD. Connect the Thunderbolt cable to the iMac. . Now I can’t remember if trim gets enabled automatically or you have to enable trim from terminal. I think the command is sudo trimforce enable
 
OP wrote:
"Now if I could somehow entire TRIM was enabled on the external USB drive. I've heard mixed things about that actually working."

It's doubtful you can get TRIM working over USB3.
But... I suggest that you stop worrying about this.

I booted an ran my 2012 Mini for six years using a SATA SSD in a USB3/SATA docking station, without TRIM, and it ran fine all that time.

It's still running fine "on the back table" as my "backup Mini"...
 
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