Booting from a superduper clone of a fusion drive

[bill272]

Hi
I am going to boot from a external ssd evo870 (made for internal) with a sata usb-c cable containing a superduper clone of a sierra osx, to a 2017 imac thunderbolt port.

When I boot from this external drive, will the mac still be using the fusion setup with the flash storage (and original hdd) still in place in the imac?

That is using the internal 32 Go flash storage part of the old fusion and the new external clone of sierra.

If yes, can I just leave things as they are and keep using the external ssd, without doing any fusion modifications? Is it going to run fast and smooth?

or do i need to modify the fusion with this new setup, for it to work fast and smooth.

I am just looking for a simple way to get things working, it doesnt have to be perfect,
But if something needs to be fine tuned i would like to know what my options are, so i can choose what to do.
Thank you

 

[Slydude]

I have a 2015 iMac with a fusion drive. I've booted it from clones almost from the day I got it, including under Sierra IIRC, with few issues as long as the clone completes properly. I have used Carbon Copy Cloner to make the clone but there's no reason a Super Duper clone won't work as also.

If I understand your question you want to know whether you need to the fusion drive, such as separate the SSD from the rest of the drive, in order for this to work. If that's the case, the answer to this question is no you don't have to do that.

For about the last year or so I've run an external clone from an SSD as the primary (boot) drive on that machine. I haven't noticed a performance slowdown compared to the Fusion drive.

 

[bill272]

hi, thank you for your answer
yes i am wondering if my new ssd will still be working as a fusion drive with the internal flash drive, if for instance I name my new ssd with the name of the old HDD.
So is this what will happen ? or does my new ssd imply that now the old fusion (old HDD and flash) setup is broken and i am using the new external ssd on its own without any fusion activity ?

I just want to be sure what is happening, because I would prefer to use the new ssd on its own boot with it and use it right away, and avoid some complicated terminal functions to play around with the fusion.

Also, this is a 2017 imac, if the flash drive will still be used with my external ssd by default, how many years do you think this flash will last?
thanks

 

[Slydude]

hi, thank you for your answer
yes i am wondering if my new ssd will still be working as a fusion drive with the internal flash drive, if for instance I name my new ssd with the name of the old HDD.
So is this what will happen ? or does my new ssd imply that now the old fusion (old HDD and flash) setup is broken and i am using the new external ssd on its own without any fusion activity ?

I just want to be sure what is happening, because I would prefer to use the new ssd on its own boot with it and use it right away, and avoid some complicated terminal functions to play around with the fusion.

Also, this is a 2017 imac, if the flash drive will still be used with my external ssd by default, how many years do you think this flash will last?
thanks

As far as I can tell from my experience, the existing Fusion drive remains intact and is untouched. The boot process seems to run entirely off of the SSD without relying on the Fusion drive at all. Perhaps others can confirm this.

I haven't looked for data recently on the longevity of Fusion drives. Some users have apparently had issues with these drives but I haven't. My 2015 iMac was my primary machine until about a month ago and it's still going strong. I switched because I had the opportunity to pick up an M1 Mac Mini cheap from a buddy.

Like all drives, the Fusion drive will eventually fail but booting/running from the external SSD should prolong that life since it doesn't need to use the Fusion drive.

 

[bill272]

ok thanks for the information,
I will try this.

 

[bill272]

Hi,
I read this in a forum
If the HDD dies, you still lose the fusion drive (which is a virtual volume that uses both drives)
Depending on the type of failure, the bad drive may affect your system where it needs to be removed. Using an external drive may not help if the internal HDD has failed.

Does that mean i should start using my external boot BEFORE the hdd dies?
Thanks

 

[Slydude]

When I first started cloning the boot drive my intention was token the clone around for emergencies. In the event of a problem I would have been able to boot from a backup and get back up and running quickly. Eventually I started boosting/running from the clone and updated the internal drive as needeed (OS updates, new software added to the clone was also added to the internal drive, etc).

Booting/running from the clone and using it as the primary drive is probably the best way to avoid the problem that concerns you. I'm going to do a bit of digging and see if I can find a more specific answer to your question. I'm not sure what Fusion drive failure would prevent booting from the external drive/clone if the clone is booting properly otherwise.

 

[MacInWin]

A Fusion drive failure should not impact the boot from external drive. Intel Macs are easily booted from external drives, even with NO internal drive available.

For Bill272, the real issue with Fusion drives is that they are just that, a fusion of a small SSD and a large rotating drive. In general, the SSD is used to boot, to be quick at that, and the RDHD is used for storage. However, that general rule is NOT absolute, and if either component fails, or if the fusion is "broken" then what is left is unbootable. However the data on the RDHD may be salvageable, depending on how the Fusion drive actually failed.

 

[Slydude]

Thanks for that update. That's what I thought would happen but it has been quite a while since I worried about that so I didn't trust my memory.

 

[MacInWin]

Sly, it's the Apple Silicon (Mx) Macs that can't boot if the internal storage is bad. Intel machines don't have that problem and can boot from external with no issue, assuming no other hardware issues.

 

[Slydude]

That's what I thought but it has been quite some time since I read the ins and outs of what can/can't be done when a Fusion drive fails. Once I knew I had a working method for creating clones I stopped thinking about failure of the Fusion drive.

The only time i was a little worried about booting from a clone is when I went to boot from one and discovered that the clone had not completed properly and wasn't bootable. It wasn't a major issue since I could have reinstalled the OS and reloaded apps and data from a backup. It would have been a much longer process though than booting from the clone and being up an running in minut0es.