Corrupt iMac Fusion drive?

[mikehalloran]

Update, I placed the 850 into another dock and the CRC error count is identical. Time to talk to Samsung.

I downloaded DriveDX. It doesn't tell me anything new but looks very good, especially for the price and includes CRC data. It won't run a "long test" without purchase but that's ok as I have TTP. Long tests can be useful for HDDs but short tests and SMART tell you what you need to know.

It generated an error message for one of my SSDs that I know isn't an issue—interesting, I suppose.

 

[mikehalloran]

Is the fusion drive that slow? Is it faster to run mainly from the internal 128GB blade ssd?

Again, there is no chance that both original drives are performing as they should after 7+ years.

Heat is the mortal enemy of late 2009–2013 iMacs with mechanical hard drives. Besides the drive life, it's the reason for GPU issues. Failing batteries masquerade as failed GPUs, BTW and 7 years is pushing that, too.

Replace both drives with one SSD. Throw away the blade. Replace the battery.

On a 2012, both busses are SATA III so there is no speed difference which buss you use but it's less expensive to replace the big one. You can install up to a 4TB SSD — 2TB will cost $203. Only if you need more than 4TB storage inside (does anyone?), then also replace the blade with a second SSD and the special harness to connect to the socket.

Besides the drive, you'll need the OWC temp sensor, a tape kit, a plastic pizza wheel and a couple of torx drivers if doing it yourself —
2012 iMac SSD install kit

This bracket isn't really necessary —double-stick tape works—but this lets your iMac run cooler.
iMac SSD bracket

Again, absolutely replace the NV RAM battery — it's time. A standard CR2032 medical/electronics battery works fine since you will be replacing the high-heat HDD. If you want the high-heat BR2032 version that Apple uses, you can get a pair from Amazon. Electrically, they are the same.
BR2032

or you can have it installed for $75–100 including data transfer depending where you live.

I'm a experienced tech who has taken care of hundreds of iMacs in schools and businesses. I was asked to weigh in on this thread and I've done so. I will not look at it again. You can keep a 2012 going for a long time by getting rid of that spinning heat pump inside.

I'm done here.

 

[davidlv]

Is the fusion drive that slow? Is it faster to run mainly from the internal 128GB blade ssd?
I have a late 2012 27” iMac coming that has a 1TB fusion drive setup. The os is only installed on the 128GB ssd and is not setup as a fusion drive. I was curious about leaving it as is or recreating the fusion drive.
i also have an extra 500GB ssd that I could connect with a USB3/Thunderbolt case that I have.

Actually, I did not feel like the Fusion drive was much slower than the separate SSD drive, maybe just a little at times. As long as you have a total of less data than the size of the SSD, the speed should be roughly the same, as everything gets loaded on the SSD first, and off-loaded to the HD if the data is not accessed much. This happens "behind-the-scenes" and it is not on a file by file arrangement. Only Apple knows how it actually works, I assume, although someone may know more about that.
Using that SSD you mentioned in the thunderbolt case would probably be the best option by far, a lot faster than the SATA III original SSD blade and Trim works in that case - it doesn't work using the USB 3 interface (use: sudo trimforce enable in terminal and follow the resulting prompts). You probably need Apple's Thunderbolt 2 to Thunderbolt 3 adapter too.

 

[TwoH]

Besides the drive, you'll need the OWC temp sensor, a tape kit, a plastic pizza wheel and a couple of torx drivers if doing it yourself —
2012 iMac SSD install kit

Intsalling a 2.5" SSD in any of the slim models of iMacs does not require an OWC temp sensor -- only if you are replacing it with a HDD that is not Apple/with built in temp sensor, or if it's a 2011.

 

[smbu2000]

Actually, I did not feel like the Fusion drive was much slower than the separate SSD drive, maybe just a little at times. As long as you have a total of less data than the size of the SSD, the speed should be roughly the same, as everything gets loaded on the SSD first, and off-loaded to the HD if the data is not accessed much. This happens "behind-the-scenes" and it is not on a file by file arrangement. Only Apple knows how it actually works, I assume, although someone may know more about that.
Using that SSD you mentioned in the thunderbolt case would probably be the best option by far, a lot faster than the SATA III original SSD blade and Trim works in that case - it doesn't work using the USB 3 interface (use: sudo trimforce enable in terminal and follow the resulting prompts). You probably need Apple's Thunderbolt 2 to Thunderbolt 3 adapter too.

The USB3/Thunderbolt case is TB1 I believe (didn't see any mention of TB2 when I bought it way back), so it works fine with just an older TB cable. I used it a long time ago as my boot drive when I had a 21" late 2013 iMac that just had a 1TB 5400rpm HDD.

Anyway, I got my 2012 27" iMac and the performance seems pretty good, so far having Mojave installed on just the 128GB blade ssd. I might try the fusion drive just to see how it performs.
Later I might open it up later and install an SSD/upgrade the wifi card to AC.

The 2012 I picked up is pretty well upgraded already with the i7-3770/32GB RAM/2GB GTX 680MX.

 

[mikehalloran]

Using that SSD you mentioned in the thunderbolt case would probably be the best option by far, a lot faster than the SATA III original SSD blade

100% wrong on a 2012. SATA III is your bottleneck.

Intsalling a 2.5" SSD in any of the slim models of iMacs does not require an OWC temp sensor -- only if you are replacing it with a HDD that is not Apple/with built in temp sensor, or if it's a 2011.

Try it on a 2012. When the fans go full on, open it back up and install the temp sensor. Not needed on a 2015, crap shoot on a 2014.

I've done many of these and by that, I mean a lot.

 

[TwoH]

Try it on a 2012. When the fans go full on, open it back up and install the temp sensor. Not needed on a 2015, crap shoot on a 2014.

It's only on the 2011 iMacs that your fans will ramp without it.

 

[mikehalloran]

It's only on the 2011 iMacs that your fans will ramp without it.

Doubling down on the wrong answer doesn't make you right.

Using the OWC sensor ensures that the fans work properly afterward. Nothing else does except finding certain HDDs with the sensor built in. Since that maintains an unacceptable internal heat level, I don't consider it a viable solution.

Disabling the drive sensor will cause the fans to roar full on under some circumstances in a 2012–2015. The 2015 is less susceptible to this and so I leave it out, telling the client not to run certain apps and utilities (that they'll never use anyway). Software hacks, unfortunately, require that you control all the fan sensors manually. Again, unacceptable.

 

[TwoH]

Doubling down on the wrong answer doesn't make you right.

Sorry but I'm not doubling down on the wrong answer lol, simply try putting a 2.5" SSD into any of the slim model iMacs (obviously excluding the iMac Pro).
Without the OWC cable, the iMac won't ramp up -- if however you use a HDD with no built-in temp sensor, it will ramp up.

 

[mbosse]

[...]One more thing. You cannot access SMART data over USB, only SATA, eSATA, PCI and Thunderbolt.

There is a small extension which indeed allows you to access SMART data also on external USB-attached enclosures - SAT SMART Driver:

DriveDx - external USB and FireWire drive diagnostics support

binaryfruit.com

It does not only work with Drive DX, but also with other SMART monitoring tools such as SMARTReporter.

Best,
Magnus

 

[davidlv]

100% wrong on a 2012. SATA III is your bottleneck.

Is there any other choice available? Fast PCIe drives are available for the cMP machines, but what is there on the market that will not be a bottleneck for connecting to the 2012 iMac's thunderbolt port?

Edit: Saw this post;

Boot from SSD on iMac with faulty HD

Hey guys I've got a 2010 iMac with a faulty HD. The Mac does not boot anymore. I went to the genuis bar and they did a diagnostics scan and it showed the HD is dead. Opening the Mac to install an SSD will cost me over 400€ Is there any way I can use and external SSD, install the OS on it, and...

forums.macrumors.com

Post #7
"IF it's a 2012 iMac
and
IF it has USB3 ports
then
You can buy a USB3 SSD, plug it in, and set that up to be the new boot drive.
It won't be as fast as the new iMacs, but it will actually run quite well, and I fearlessly predict that you'll be quite happy with that solution."

 

[Gogh Apple]

That didn’t work for me, but this did.

From Terminal: diskutil cs list

Write down or copy ‘Logical Volume Group’: identifier

Then: diskutil coreStorage delete “identifier from above”

“identifier from above” = just exact numbers and letters

Ex: diskutil coreStorage delete BB99RG-88FT-7U77-277T-JI765T8T9667

Boom! 2 blank drives after a minute.

 

[mikehalloran]

Is there any other choice available? Fast PCIe drives are available for the cMP machines, but what is there on the market that will not be a bottleneck for connecting to the 2012 iMac's thunderbolt port?

Edit: Saw your post on;

Boot from SSD on iMac with faulty HD

Hey guys I've got a 2010 iMac with a faulty HD. The Mac does not boot anymore. I went to the genuis bar and they did a diagnostics scan and it showed the HD is dead. Opening the Mac to install an SSD will cost me over 400€ Is there any way I can use and external SSD, install the OS on it, and...

forums.macrumors.com

Post #7
"IF it's a 2012 iMac
and
IF it has USB3 ports
then
You can buy a USB3 SSD, plug it in, and set that up to be the new boot drive.
It won't be as fast as the new iMacs, but it will actually run quite well, and I fearlessly predict that you'll be quite happy with that solution."

So that seems to be contradictory to your post #31 here in this thread: "100% wrong on a 2012. SATA III is your bottleneck." where I suggested using a external thunderbolt case with an SSD inside. (and of course Trim will work in a thunderbolt case and not work in a 3 case)
So if you "fearlessly predict that you'll be quite happy with that solution." with a USB external drive, an external thunderbolt solution should be even better given the Trim situation. Don't you think so?

I just saw this… You made a mistake. Those were not my quotes. I stand by what I actually posted. Another user likes to "fearlessly predict", not I. Please be more careful.

 

[davidlv]

I just saw this… You made a mistake. Those were not my quotes. I stand by what I actually posted. Another user likes to "fearlessly predict", not I. Please be more careful.

That post was from Jan 28, 2020
more than 3 years ago. Granted, it wasn't your post. edited now.