Using old iMac Fusion drive as external

[imac275]

I have recently replaced my 2012 iMac with a 2017.

My Photos Library would not restore to the new iMac using Migration Assistant, but I have now got most of the files across. Some do appears to be missing from the backup, even though they exist on the original iMac.

I can't use the original iMac because the display has failed and it also won't output to an external display.

What I'd like to do is use the original Fusion Drive in a caddy and download any new files from it. Is it possible to do this using just a standard 3.5" external caddy or do I need something different given it has the SSD portion as well?

 

[Fishrrman]

The fusion drive -is not- a single, physical drive.
It's TWO separate drives:
1. An SSD flash drive
and
2. A platter-based hard drive

"Fusion" is software which "melds" the two physical drives to appear "as one" in the finder.
So... you can't "take it out of" the old iMac and use it in a caddy.

Further, because the drive is created "in software", you can't "separate" the two drives. You could take the HDD out of the old iMac, but everything on it would be lost, because -- again -- the "drive" is created in software on the old iMac.
Nothing would be "recoverable".

 

[imac275]

The fusion drive -is not- a single, physical drive.
It's TWO separate drives:
1. An SSD flash drive
and
2. A platter-based hard drive

"Fusion" is software which "melds" the two physical drives to appear "as one" in the finder.
So... you can't "take it out of" the old iMac and use it in a caddy.

Further, because the drive is created "in software", you can't "separate" the two drives. You could take the HDD out of the old iMac, but everything on it would be lost, because -- again -- the "drive" is created in software on the old iMac.
Nothing would be "recoverable".

Thanks. That is exactly what I was hoping wouldn't be the case, but I suspected it might be.

It looks as though I will have to persevere with trying to get the old machine working. It certainly provides a good reminder to me to get CCC up and running again rather than relying on Time Machine/Migration Assistant alone for backup.

 

[J.Gallardo]

I have recently replaced my 2012 iMac with a 2017.

My Photos Library would not restore to the new iMac using Migration Assistant, but I have now got most of the files across. Some do appears to be missing from the backup, even though they exist on the original iMac.

I can't use the original iMac because the display has failed and it also won't output to an external display.

What I'd like to do is use the original Fusion Drive in a caddy and download any new files from it. Is it possible to do this using just a standard 3.5" external caddy or do I need something different given it has the SSD portion as well?

I have exactly the same problem... Mine was a "late 2009" iMac, wich still works, but no gpu. I'm getting a 2017 iMac, and migrating content is no so easy in this situation.
I can recover the internal hd, as is a no-fusion. But my first thought was about using apple's wonderful "target disk mode". It works just with FireWire or Thunderbolt, so the problem is linking it to the 2017 iMac.
Target Disk mode seems ideal in your situation, if your old mac is able to start with the t key pressed...
You could manage your old hd as an external unit, wich was a big Apple advantage... I feel this characteristic is being forgotten; a pity.

 

[imac275]

I have exactly the same problem... Mine was a "late 2009" iMac, wich still works, but no gpu. I'm getting a 2017 iMac, and migrating content is no so easy in this situation.
I can recover the internal hd, as is a no-fusion. But my first thought was about using apple's wonderful "target disk mode". It works just with FireWire or Thunderbolt, so the problem is linking it to the 2017 iMac.
Target Disk mode seems ideal in your situation, if your old mac is able to start with the t key pressed...
You could manage your old hd as an external unit, wich was a big Apple advantage... I feel this characteristic is being forgotten; a pity.

That's great, thanks.

I have found an article about it:

https://support.apple.com/en-gb/HT201462

It seems to go through a lot of steps that would require a screen, but I assume that this is bypassed if I start the machine with the T key pressed?

As you say, cable choice might be a problem. It seems that TD mode works with USB-C as well as Thunderbolt and Firewire, so I might be able to use some type of adaptor.

 

[J.Gallardo]

That's great, thanks.

I have found an article about it:

https://support.apple.com/en-gb/HT201462

It seems to go through a lot of steps that would require a screen, but I assume that this is bypassed if I start the machine with the T key pressed?

As you say, cable choice might be a problem. It seems that TD mode works with USB-C as well as Thunderbolt and Firewire, so I might be able to use some type of adaptor.

Starting with the T key pressed should work; you just (would) see a big FireWire sign moving around (I don't know using Thunderbolt... Maybe the attached cable is recognized?), and after that you have a "normal" external drive. This trick has allowed me to repair an old mac internal hd or repair system files from an external mac with the appropriate soft tools. I hope to be able to recover info this way, this time, as seems quicker than pulling out the hd. And Fusion Drive, as it's been said, is no easily recovered.

Other way to connect two macs is with Migration Assistant. This allows for other connection methods (ethernet, usb...) BUT Migration Assistant needs to be running in both macs, and be attended.
In your situation, perhaps a Thunderbolt 2---->Thunderbolt 3 cable should be enough to use Target Disk mode. Not in mine, as "late 2009" only offers Firewire as Target Disk mode connection.
Anyhow, I know all this by reading on the net... including this forum. I'd like some advice from someone knowing about this.