Internal vs External SSD for M4 iMac

[retiredInDelaware]

I am considering purchasing a M4 iMac with 24 GB of memory and 512 GB SSD storage. This is a configuration that I can buy at resellers besides Apple. I actually need around 2 TB of SSD storage, but I can only get that configuration from Apple and it adds $600.00 to the price for the addition 1.5 TB. I see that OWC sells external Thunderbolt 4 SSD drives, $469.99 for 2TB or $649.99 for 4TB. I'm looking for technical reasons to get the internal SSD vs external SSD drive. How much of a speed difference will I see reading/writing to the external SSD? I know that Apple charges too much for SSD upgrades, but if there is a technical advantage I will consider it. Thanks for any information you can provide.

 

[Bigwaff]

You don’t mention your computing activities or workloads. Normal, everyday computing activities, you won’t notice the difference between internal/external. Perhaps you should be asking whether you need the power of M4. An iMac M3 512/24 can be had on the Apple refurb store for $400 less than similarly spec M4. Or search around, M3 iMac stock will be heavily discounted this holiday season.

 

[Pagemakers]

I’m in the same boat…. M4 mini with 256GB and a 1TB external or M4 mini with 1TB internal.

I’m a non-gaming “normal” everyday user.

Would I notice any difference in general day to day use?

 

[Fishrrman]

Remember that if you get an external SSD to serve as "secondary/external" storage, you will now have TWO drives that require backup:
- internal SSD
and
- external SSD.

Not necessarily "a problem", but still something that should be considered.

 

[Pagemakers]

A Curveball question. I understand the front M4 mini ports are slower than the rear. To prevent using all 3 rear ports if I have 3 Apple SD screens, can the SD’s be daisy-chained to free up the faster ports for external SSD usage?

 

[justmadeupname]

Remember that if you get an external SSD to serve as "secondary/external" storage, you will now have TWO drives that require backup:
- internal SSD
and
- external SSD.

Not necessarily "a problem", but still something that should be considered.

Never thought of that, thanks ! 👍

 

[PaulD-UK]

@Pagemakers Thunderbolt 3 NVMe enclosures with two TB ports can be daisy-chained from the TB4 rear ports.
The Mac mini's front USB 3.1 Gen 2 ports can have a hub plugged in to allow more than one USB SSD share the 10MB/s bandwidth.

Thunderbolt 3 docks plugged into the rear TB4 ports can pass through the ASD monitor connection, and allow USB 3.1 SSDs to plug into USB ports on the dock. The SSDs will be as fast as they are if plugged into the front ports.

A TB4 dock plugged into the rear TB4 ports work the same, but as well as an ASD, you can plug in TB3 NVMe enlosures which will have a slightly lower write speed, but still a faster connection than USB SSDs.
For that you need a TB4 dock with multiple TB output ports.

TB3 enclosures, if they have two TB3 ports, can be daisy-chained, sharing the connection bandwidth.

TB4 enclosures don't really exist, as they are USB4, which will work with TB3 ports, but can't be daisy-chained.
There are TB3 enclosures that are labelled TB4, but can only work at USB 3.1 speeds if connected to a USB port.

 

[Pagemakers]

Thank you for taking the time to write such a comprehensive reply. Very helpful.

 

[wilberforce]

I have a new M4 iMac with 2TB SSD. I get about 3000 MB/s read/write using Blackmagic disk speed test with 5GB test.
Not as fast as machines with Pro or Max chips (which often achieve in the order of 5000 MB/s)
Just FYI

 

[retiredInDelaware]

You don’t mention your computing activities or workloads. Normal, everyday computing activities, you won’t notice the difference between internal/external. Perhaps you should be asking whether you need the power of M4. An iMac M3 512/24 can be had on the Apple refurb store for $400 less than similarly spec M4. Or search around, M3 iMac stock will be heavily discounted this holiday season.

The main reason that I need 2 TB of disk space is I already have almost 1 TB of photos. I was considering locating them all on an external drive, that way I could keep adding SSDs as I needed. I could consider having them in the cloud, but I like having them on my own physical media. Besides the photos, I mainly use my current iMac for email, web browsing, word processing, and spreadsheets. I try to keep my computers as long as possible, that's why I am considering the M4 iMac - getting the longest support. I currently have a late 2015 27" iMac that is on Monterey 12.7.6. I may look for a deal on a M3 iMac. Thanks for your response.

 

[retiredInDelaware]

I have a new M4 iMac with 2TB SSD. I get about 3000 MB/s read/write using Blackmagic disk speed test with 5GB test.
Not as fast as machines with Pro or Max chips (which often achieve in the order of 5000 MB/s)
Just FYI

Thanks for that information. Since the Thunderbolt 4 port is 40 GB/second it shouldn't be a bottleneck to an external SSD - unless I'm looking at this too simplistically.

 

[wilberforce]

Thanks for that information. Since the Thunderbolt 4 port is 40 GB/second it shouldn't be a bottleneck to an external SSD - unless I'm looking at this too simplistically.

40 Gb/s, not 40GB/s, and actual data throughput is about 22 Gb/s, which is about 2800 MB/s.
Consider also that the real speed of an external SSD is often about half its advertised speed.
To get near 3000 MB/s real life speed from an external SSD could cost more than the internal SSD upgrade. However for a reasonable cost it will not be too much slower. There will be little overall computer performance difference between 2000 and 3000 MB/s

 

[retiredInDelaware]

40 Gb/s, not 40GB/s, and actual data throughput is about 22 Gb/s, which is about2800 MB/s.
Consider also that the real speed of an external SSD is often about half its advertised speed.
To get near 3000 MB/s real life speed from an external SSD could cost more than the internal SSD upgrade. However for a reasonable cost it will not be too much slower. There will be little overall computer performance difference between 2000 and 3000 MB/s

Thanks for catching my error on data throughput. I'll probably end up getting the 2 TB SSD internally and the OWC or similar external for backups.