Big Sur on a Fusion Drive

[mac98aop]

Hello

I've a 27" 2017 iMac  with 1TB Fusion.

Will Big Sur behave?

Thanks

[Sam - MacAmbulance]

Fusion drive performance seemed to take a nosedive in Catalina, maybe Big Sur’s different. I’d still replace the spinning disk drive with an SSD anyway just for more speed and less noise.

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Regards Sam Mullen +44 (0)7747778022 in...@macambulance.com www.macambulance.com MacAmbulance Ltd. Providing Affordable Mac/PC Support and Web Development

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[mac98aop]

Thanks, Sam. I realise it's not quite a 'plug and play' to replace with an SSD. I guess I'm just first someone else is running Big Sur on a fusion drive and quite happy with performance (this is our family machine, so it's web surfing, email, Pages, Keynote, Photos... that's about it - but I'd hate it to snarl up)

AP

[Sam - MacAmbulance]

You’d need to : 

• Clone the data on the drive to an external drive
• Cut open the iMac
• Replace the HDD with an SSD, using a 2.5” - 3.5” adapter bracket and installing a thermal sensor to keep the fans happy
• Glue it all back together
• User diskutil cs resetfusion
• Boot from the external drive and clone the data back to the new fusion drive.

I do about three a week, really makes a huge difference to speed.

_

Regards Sam Mullen +44 (0)7747778022 in...@macambulance.com www.macambulance.com MacAmbulance Ltd. Providing Affordable Mac/PC Support and Web Development

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[Tony Crooks]

I’d avoid updating to Big Sur with a fusion drive. This has failed for a number of iMac users to date although rebuilding the fusion drive seems to overcome the problem ( not aware what is required to do this other than it requires use of the Terminal app).

You can check on this on the Apple Community Forum in Apple's Support pages.

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Tony Crooks
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+44 7428 706227

[mac98aop]

Ok, thanks Sam and Tony.

I'll peruse the Support pages and see what's what. 

And I won't be installing the SSD myself, Sam, it sounds terrifying - but might be the way to go with experienced expert! I did my MBPro as you advised a while back, but that was easy in comparison!

Adam

[mac98aop]

And I still feel optimistic that Big Sur should work on a Fusion Drive. Hate to think it's been left behind when it's really still far from old/obsolete. I know it's all about SSD now, but perhaps I'm being too optimistic.

At least if it bricks the iMac, it'll be up to Apple to resolve?! Even without warranty, if an Apple OS update ruins an Apple machine that it's released for, I'd like to think they'd help out?! 

[Martin]

I don't know if anyone uses TechTool Pro 13. It doesn't work with Big Sur. I've asked them on the Micromat Forum and Micromat says its my fault for not checking compatibility and it wasn't their job to warn their customers i.e. by sending out an email

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[Philip Tomlinson]

Hi

This is interesting. I have a Fusion drive iMac 🖥 I’ve very recently installed Big Sur and I was pleased with the result. It seems to be marginally faster at opening up apps and performing most operations. 

I didn’t know that Catalina had a bad reputation running on a Fusion drive, but I was frustrated with some delays and glitches!

Phil T

Sent from my iPad

On 20 Nov 2020, at 16:07, Sam - MacAmbulance <in...@macambulance.com> wrote:

Fusion drive performance seemed to take a nosedive in Catalina, maybe Big Sur’s different. I’d still replace the spinning disk drive with an SSD anyway just for more speed and less noise.

To view this discussion on the web, visit https://groups.google.com/d/msgid/smug/F8425280-0471-4693-9118-746EBC3CF5A4%40macambulance.com.

[Jason P. Davies]

Fusion drives have an SSD *part* so I would expect it to work ok. I’m no expert on them though.

Thanks,

-Jason
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[Tony Crooks]

It may be an installer issue. I’ve read that the Big Sur installer seems to want to rebuild the fusion drive in APFS format and has problems doing this properly in some circumstances. This may be something to do with keeping Big Sur in a separate container on the SSD. If I understood it correctly the installer creates a new container for Big Sur and when the OS is installed it wants to remove the previous OS by deleting the container. Reading that those who have erased their fusion drive and done a ‘clean install’ have had success, copying apps and user accounts back after the clean install has finished. But we all do clean installs every time, don’t we? I’m sure that was a Sam recommendation.

[Jason P. Davies]

Clean installs are definitely better option but then again the last time I did one was um 10.0.0

Cheers,

-Jason
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[Sam - MacAmbulance]

The annoying thing about recent Macs, especially 21.5” models, was that the SSD part of the Fusion Drive was only 26GB, so it fills up very quickly and any speed benefit is lost when larger apps have to be stored on the hard drive part.

I’ve set up over 25 iMacs with SSD+SSD fusion drives in the last few months, the speed increase is incredible. 

_

Regards Sam Mullen +44 (0)7747778022 in...@macambulance.com www.macambulance.com MacAmbulance Ltd. Providing Affordable Mac/PC Support and Web Development

MacAmbulance Ltd. is a registered company in England & Wales, registration number 8466597 This email is intended solely for the addressed recipients and may contain privileged or confidential information. If you have received this email in error please notify the sender and delete the email immediately.

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[Jason P. Davies]

Wait, what’s the point of SSD plus SSD fusion? Or is it that you swap a different physical artefact and leave the original Ssd component intact?

Thanks,

-Jason
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On 21 Nov 2020 at 15:32:41 GMT, Sam - MacAmbulance <in...@macambulance.com> wrote:

The annoying thing about recent Macs, especially 21.5” models, was that the SSD part of the Fusion Drive was only 26GB, so it fills up very quickly and any speed benefit is lost when larger apps have to be stored on the hard drive part.

I’ve set up over 25 iMacs with SSD+SSD fusion drives in the last few months, the speed increase is incredible.
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Regards
Sam Mullen

+44 (0)7747778022 <tel://+447747778022>
in...@macambulance.com <mailto:in...@macambulance.com>
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[Sam - MacAmbulance]

A couple of reasons

• It’s less confusing for the user to have two distinct volumes on the desktop, like Macintosh HD and 26GB Internal Flash
• The internal flash drive, even if it’s 26GB, is PCIe, so is faster than the SATA connected SSD drive. Might as well make use of that extra speed for OS & apps, then the run-off data can be stored on a nearly-as-fast SSD

The downside is that if one SSD fails, you lose all the data, but that’s true of an HDD/SSD Fusion Drive and less likely with two SSDs

_

Regards Sam Mullen +44 (0)7747778022

in...@macambulance.com www.macambulance.com

MacAmbulance Ltd. Providing Affordable Mac/PC Support and Web Development

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[Philip Tomlinson]

That’s very interesting Sam. Are you saying that you can replace a fusion drive in an iMac by installing a second SSD? 

Phil

Sent from my iPad

On 21 Nov 2020, at 15:32, Sam - MacAmbulance <in...@macambulance.com> wrote:

The annoying thing about recent Macs, especially 21.5” models, was that the SSD part of the Fusion Drive was only 26GB, so it fills up very quickly and any speed benefit is lost when larger apps have to be stored on the hard drive part.

To view this discussion on the web, visit https://groups.google.com/d/msgid/smug/E47211FA-BAF1-4FD7-8D19-E8DEED7A77D4%40macambulance.com.

[Sam - MacAmbulance]

You can replace the spinning disk drive part of the Fusion Drive with an SSD yes

_

Regards Sam Mullen +44 (0)7747778022 in...@macambulance.com www.macambulance.com MacAmbulance Ltd. Providing Affordable Mac/PC Support and Web Development

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