Are external SSD not made to be used as the boot disk? My speed is beyond slow.

SergioQ wrote:

Thank you, but making the SSD my boot drive was not my issue. It's the slowness it has under certain operations that the internal SSD doesn't have

Understood.

Try a different port, try a different cable connection, try a different enclosure

all these have will affect transfer speed...

OWC/MacSales has Thunderbolt drives/ enclosure if your "Crucial X9 2TB Portable SSD " is inadequate.

Thunderbolt External Drives from OWC Achieve speeds up to 2800MB/s 

https://www.crucial.com/ssd/x9-pro/ USB 3.2 Gen Speed & timing 1050MB/s 

MacBook Pro 16" 2019 Your internal ssd is soldered to the board...

BlackMagic reference, real world test:

Write Speed 2825 MB/s with highest at nearly 2850 MB/s

Read Speed (average over multiple tests): 2625 MB/s 

Is your external SSD formatted to APFS?

SergioQ wrote:

None of this happens if I boot up off the internal HD.

...

MacBook Pro 16" 2019

That machine comes with a 512 GB hard drive, which is more than adequate to run the OS and Xcode.

Find those other 300 GB that you don't need on the internal drive and move those to the external.

SergioQ wrote:

Mac specs below

I recently bought a Crucial X9 2TB Portable SSD because my internal HD was short on available space (Xcode and developer files took most of the space). I was able to make the ext. SSD my boot drive.

First thing I realized was that my Mac took much longer to boot up. That I figured I could deal with.

Other than that I noticed no other speed lags. That is until I ran Xcode (a development program).

What I noticed was when that when Xcode ran its iPhone simulator the system was so slow that I would eventually lose my WiFi. Not the connection itself, but WiFi no longer worked. Not just that, but when I ran the WiFi diagnostics (from the OS) it could not write its report to disk. Eventually it would just say unable to write.

None of this happens if I boot up off the internal HD.

I did a lot of rebooting and testing, and this all seems to come down to using the external SSD as the boot disk.

Are there SSDs that aren't made to be boot drives? Does anyone have any experience in this at all?

Am at a complete standstill work wise until I figure this out.

Thank you

MacBook Pro 16" 2019

Processor 2.6 GHz 6-Core Intel Core i7

16GB

Mac OS Sonoma 14.2

This is a Ventura article —still seems applicable for Sonoma

T2 chip Intel 2019 MBP 16"

https://appleinsider.com/inside/macos-ventura/tips/how-to-make-an-external-bootable-working-drive-in-macos-ventura