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Upgrading Fusion Intel iMac : most cost effective use of SSD. Advice please.

I am considering a speed upgrade converting my iMac 2019 5K to SSD and I seek advice regarding choice between NVMe/SSD and or replacement of internal SATA HDD with internal SATA/SSD.


I have read the installation procedures and am not fazed with the task as I have previous experience upgrading G2 processor and graphics card, and installing optical and HDD in 24" iMacs. I recognise installing an SATA/SSD is clearly less complicated than an NVMe PCIe blade. But I will do this once only and wish to get it right.


Am I correct in believing the entire computer o/s and data can reside on a 1TB blade NVMe PCIe Gen3 M2 SSD (in my case), just like any other drive? My impression is that the Apple o/s and all data files can be driven from that one NVMe/SSD formatted as APFS just as any type of drive. Further, I get the impression it will be cheaper and

out-perform a comparable 1TB internal SATA/SSD replacement of the Fusion HDD. My understanding is the PCIe Gen 3.0 has a higher speed of operation than the SATA/SSD.


A kit is attractive way to go but I get the impression this may be expensive in terms of cost per GB. However some Kits are Mac orientated in choice of SSD whereas purchasing individual NVMe drives can, I read, in some cases be uncertain regarding compatibility.


Given I have yet to find an article which addresses upgrading issues from these perspectives I would welcome comments and advice regarding NVMe vs SATA/SSD disk speeds and cost effectiveness


Many Thanks.






Posted on Nov 6, 2022 1:38 AM

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Posted on Nov 8, 2022 5:35 AM

Keep in mind that the macOS 12.x installer refused to install for the first time when no Apple internal drives were available. I haven't heard whether the same happens with macOS 13.x Ventura probably since very few Macs capable of running Ventura actually have non-Apple internal drives. Once the macOS 12.x+ installer updated the system firmware on the first install, then later re-installs of macOS 12.x Monterey were possible with a third party drive installed internally. Just something to consider since swapping drives in an iMac is not that quick or easy.


Yes, an NVMe SSD will be faster than a SATA SSD by quite a bit. However, most people will never be able to tell the difference for most workloads. The speed differences between various NVMe SSDs will be even less. An external USB3.1Gen2 NVMe based SSD will be just as fast as an internal one (or close enough). Just make sure the USB3 SSD supports UASP as well as any adapters/docks/hubs which are connected in a direct chain to the computer for best performance. An external SSD has the luxury of being able to be re-purposed to another computer when this computer fails. An OWC Aura NVMe SSD can only be used internally within a Mac as there are no USB adapters or enclosures compatible with it. Even OWC's own enclosure which is compatible with the original Apple OEM SSD will not work with OWC's NVMe SSD....OWC has a warning saying installing the OWC Aura NVMe SSD into the OWC enclosure may damage both the SSD & the enclosure.


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Nov 8, 2022 5:35 AM in response to Terraaustralia

Keep in mind that the macOS 12.x installer refused to install for the first time when no Apple internal drives were available. I haven't heard whether the same happens with macOS 13.x Ventura probably since very few Macs capable of running Ventura actually have non-Apple internal drives. Once the macOS 12.x+ installer updated the system firmware on the first install, then later re-installs of macOS 12.x Monterey were possible with a third party drive installed internally. Just something to consider since swapping drives in an iMac is not that quick or easy.


Yes, an NVMe SSD will be faster than a SATA SSD by quite a bit. However, most people will never be able to tell the difference for most workloads. The speed differences between various NVMe SSDs will be even less. An external USB3.1Gen2 NVMe based SSD will be just as fast as an internal one (or close enough). Just make sure the USB3 SSD supports UASP as well as any adapters/docks/hubs which are connected in a direct chain to the computer for best performance. An external SSD has the luxury of being able to be re-purposed to another computer when this computer fails. An OWC Aura NVMe SSD can only be used internally within a Mac as there are no USB adapters or enclosures compatible with it. Even OWC's own enclosure which is compatible with the original Apple OEM SSD will not work with OWC's NVMe SSD....OWC has a warning saying installing the OWC Aura NVMe SSD into the OWC enclosure may damage both the SSD & the enclosure.


Nov 6, 2022 1:47 AM in response to Terraaustralia

Hello!


Why not simply use an external Thunderbolt SSD? In terms of performance, a high-quality Thunderbolt SSD, such as the LaCie 1TB Rugged SSD Pro External Drive with Thunderbolt 3 - Apple, and an internal SSD is nearly identical, and both support SMART and TRIM. Plus, there's no unauthorized modification of the iMac, and you can use the internal Fusion Drive as backup.


Jack

Nov 7, 2022 11:07 PM in response to Jack-19

Thank you for pointing out my error Jack. Yes your LaCie NVMe is about three times faster than my Samsung T7. That would certainly account for your external speed results being better than mine.

However, the TB3 cable is surely a bottleneck regarding speed? 40GB/ps really inhibits the speed potential of both your LaCie and my T7.


As I said above, the direct connection of NVMe to the PCIe/motherboard would ensure a faster performance closer to theoretical speeds than is possible with any external connection. How much faster is an open question. Your experience renders the external vs internal as similar, which is interesting given the unspectacular performance of the Apple SM0128G NVMe, and the high 3000GB/ps speed of the LaCie SSD.


Cost-wise, to get 3000+GB/ps the LaCie you describe is currently close to AUD $600. By comparison the internal OWC Aura Pro X2 NVMe running at 3000+GB/ps can be purchased around AUD $364 from Amazon AU.


In considering speed, I see three factors favouring internal over external NVMe:


  1. The internal NVMe will run close to maximum theoretical speeds, whereas the external is partly throttled by the 40GB/ps TB3 cable and by o/s drive manager.
  2. An internal OWC Aura X2 NVMe is significantly cheaper than the external LaCie 1TB TB3 although installation is labour intensive for the OWC.
  3. Making speed comparisons based on the Fusion Drive vs External should consider the Apple SM0128G is approximately 15%-55% slower than the OWC Aura X2 according to task: https://www.anandtech.com/show/14382/the-owc-aura-pro-x2-ssd-review-nvme-for-older-macs/2 On this basis fitting an internal 3000MB/ps NVMeSSD would seem to raise a Mac performance markedly above any external SSD.


As a result of your comments Jack, as a lay consumer, I have more closely examined the issues and the internal OWC NVMe appeals to me as best value for money so far. Exactly how much speed I may gain is hard to judge and the percentage needs to be considerable to be noticeable. Given the small time spans, and judging from https://www.anandtech.com figures I am guessing at average 50% faster is needed to justify the effort.


Can any reader of this blog offer insight to the speed gain of an internal NVMe running at around 3000MB/ps?



Nov 7, 2022 1:37 AM in response to Jack-19

Thank you for your response Jack.

In essense I seek to minimise desk clutter. However I have to disagree with your comment on speed of external drive. I have an external 1TB Samsung T7 connected with TB3. With Monterey as a start-up drive on the Samsung, the time was 42 seconds.

Start-up on the Fusion drive was 20 seconds.

Given the NVMe is in a PCIe slot on the motherboard with no manager or cables involved as is the case with the external drive the disparity in speed is not difficult to understand.

If you are referring to an SSD replacing the Fusion HDD it will be a SATA/SSD at 600 MB/sec. An NVMe SSD is generally quoted as four times faster than the SATA/SSD 3000+/MB/sec. The numbers are bench test speeds.

Given that the Apple NVMe is very average in speed tests, price aside, Purchasing a good quality 1TB NVMe seems to me the most obvious way to improve mac performance.





Nov 8, 2022 5:56 PM in response to HWTech

Thank you for your comments HWTech. I appreciate that embarking upon considerable labour needs to be justified with a marked speed improvement. Your comments about NVMe Gen 2 and external reflect Jack’s observation.


I am assuming the combination of Apple SM0128L and TB3 cable choking external SSD explains the similarity of your speed impressions and Jack-19’s comments.

I would have expected Jack’s LaCie to outperform Apples internal NVMe by a large margin based upon its speed and capacity.


At this stage I have no intention of replacing Apples SATA HDD. But thanks for the caution. I also very much appreciate your comments about the OWC Aura X2 particularly as it seems costly by comparison with its performance specs.



Using a Sabrent NVMe/M2 Gen 3 SSD and a Sintech NGFF Adapter card the guy replaced both NVMe and SATA drives with SSD. He happens to be upgrading exactly my model iMac 19.1 and It was most helpful that he identified the Sabrent SSD’s which proved compatible.



However the jury is still out regarding effect of speed on start-up and video file transfer.

According to Blackmagic my Write/Read speed is around 750/2500 MB/s. Given a faster NVMe at Write speed of say a Samsung Evo or Evo plus giving 2700-3000MB/s improvement, I would expect to see and feel a speed jump.


Has anyone replaced the Apple SM0128L with a fast NVMe and is prepared to comment on apparent speed improvement?


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Upgrading Fusion Intel iMac : most cost effective use of SSD. Advice please.

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