User profile for user: GraeneyMac
GraeneyMac Author
User level: Level 1
4 points

Transferring Aperture Library (90GB) from 2017 iMac to an External SSD Drive. Optimum Speeds and R/W Rates possible?

Hi.


Hi, Apple Community!


I am in the process of transferring my Aperture Library (90GB) from a 2017 iMac for back-up to an External SSD Drive and would like to know what optimum Speeds and R/W Rates are possible?


What speed could I expect with the Thunderbolt on a 2017 iMac 5K Retina 27" (running on Mojave 10.14.6) and using a Belkin 2m Thunderbolt 3 USB-USB Cable (Thunderbolt Certified 40Gbps, 5K, 100W, Type C 3.1) and the Thunderbolt 5 LaCie Pro5 SSD? 


On the System Report the Firmware version of the 2017 iMac Thunderbolt Bus is 41.4, the Link Controller Firmware Version is 0.39.0 and the Speed is 'Up to 40GB/s.


Would there be increased speed and read/write rates if i) I use a generic Thunderbolt 4 lead or ii) an Apple Thunderbolt 4 PRO lead? 


I am asking the same questions elsewhere and it's very difficult to 'pin down' a definitive answer i.e. one carried out in lab conditions.


'Connecting Rugged SSD Pro5 to a Thunderbolt 3 (Mac only), Thunderbolt 4, or USB4 port limits its performance to the port's speed.' (Seagate Compatibility)


On the Pro5 Spec it states:


  • 'Works With USB-C host: USB 40 Gbps, USB 20 Gbps, USB 10 Gbps, Thunderbolt™ 5, Thunderbolt™ 4
  • Works with iPad Pro® with USB-C
  • Operating Systems: Latest versions of Windows®, macOS®, and iPadOS®'


I'm hoping that somebody with expertise/personal experience in this area might be able to help out.


Best wishes.

iMac 27″ 5K, macOS 10.14

Posted on Apr 3, 2025 4:37 AM

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User profile for user: Tesserax
Tesserax
User level: Level 10
155,174 points

Apr 3, 2025 9:56 AM in response to GraeneyMac

As you know, your 2017 iMac has Thunderbolt 3, which theoretically supports up to 40 Gbps (5 GB/s). However, in practical usage, especially with storage, actual performance is well below that due to several factors — most importantly, drive controller limitations and file system overhead. The LaCie Rugged SSD Pro (if we're assuming this is the one with Thunderbolt 3 NVMe-level performance) can saturate Thunderbolt 3 with up to 2800 MB/s read and 2400 MB/s write in ideal conditions. However, on your iMac, you're more likely to see real-world speeds of 2000–2200 MB/s read and around 1800–2000 MB/s write, depending on the size of the files and how sustained the transfers are.


Your Belkin 2m Thunderbolt 3 cable is Thunderbolt-certified, so as long as it's rated for 40 Gbps (which it is), you won’t see much improvement switching to a Thunderbolt 4 cable, whether generic or Apple-branded. Thunderbolt 4 doesn’t increase max speed over Thunderbolt 3 — it just standardizes support and enhances compatibility/reliability across devices.


With that said, Apple’s Thunderbolt 4 Pro cable is very high quality and can sometimes reduce latency or improve signal integrity, but it won’t magically make your 2017 iMac or the LaCie drive go any faster — it’ll just ensure you're getting the best your current gear allows.

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User profile for user: GraeneyMac
GraeneyMac Author
User level: Level 1
4 points

Apr 3, 2025 4:49 PM in response to Tesserax

Hi Tesserax.


Thank you for a very insightful and reassuring reply and for responding to each question. Very helpful.


I don't know if the following information will affect somewhat your answer. The LaCie Rugged SSD Pro with Thunderbolt 3 and high-performance external NVMe SSD is the drive that you mentioned and is black in colour. The drive that I am referring to is the LaCie Rugged SSD Pro5 which is a recent addition, is blue in colour and supports Thunderbolt 5:


System Requirements


  • Interface: Thunderbolt 5​ (up to 80 Gb/s)
  • 'Works With USB-C host: USB 40 Gbps, USB 20 Gbps, USB 10 Gbps, Thunderbolt™ 5, Thunderbolt™ 4
  • Works with iPad Pro® with USB-C
  • Operating Systems: Latest versions of Windows®, macOS®, and iPadOS®'


Best wishes,


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User profile for user: GraeneyMac
GraeneyMac Author
User level: Level 1
4 points

Apr 4, 2025 11:58 AM in response to GraeneyMac

Dear Tesserax,


Are you able to comment on this system-requirements bullet point for the LaCie Rugged SSD Pro5 external HD:


'Works With USB-C host: USB 40 Gbps, USB 20 Gbps, USB 10 Gbps, Thunderbolt™ 5, Thunderbolt™ 4



Would you say that the comment below which you submitted referring to The LaCie Rugged SSD Pro (... with Thunderbolt 3 NVMe-level performance), be also applicable to the LaCie Rugged SSD PRO5?


'The LaCie Rugged SSD Pro (if we're assuming this is the one with Thunderbolt 3 NVMe-level performance) can saturate Thunderbolt 3 with up to 2800 MB/s read and 2400 MB/s write in ideal conditions. However, on your iMac, you're more likely to see real-world speeds of 2000–2200 MB/s read and around 1800–2000 MB/s write, depending on the size of the files and how sustained the transfers are.'


I would value you opinion. Being able confidently to invest in the Pro5, I might just have found the sweet spot between backwards compatibility and future proofing. Ideal of course if I could try one out live before deciding!


Thank you again and best wishes,


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Transferring Aperture Library (90GB) from 2017 iMac to an External SSD Drive. Optimum Speeds and R/W Rates possible?

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