Question Add SSD to Pi 4

Jan 24, 2021
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Tom’s article, How to Boot Raspberry Pi 4 From a USB SSD or Flash Drive - makes it look painless now to add an external SSD. I truly want to try using a Pi 4 for everyday tasks for a week - just to prove to myself how powerful a Pi can be. Is adding an external SSD and booting from it a dramatic enhancement? I have a new Kingston 2.5” 960GB that is dying to be used for something.
 
Apr 24, 2021
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What OS do you plan on using? I have a Pi4 8GB and browsing the web with Chromium is painfully slow on the official "Raspberry PI OS". Basic sites like Google are fine but anything heavy like Youtube or Netflix it really struggles with.

For custom OS installs like RetroPie or LibreLec that give you a basic menu system which has been optimised for the Pi then it performs really well, but for general purpose Linux I don't think it's quite powerful enough or the display drivers haven't been optimised enough for the Pi 4 GPU yet or whatever, so it's really sluggish. I don't think an SSD will make much difference since it seems to be the system itself that is slow on Desktop Linux.
 

kanewolf

Titan
Moderator
This is the guide I used -- https://jamesachambers.com/raspberry-pi-4-usb-boot-config-guide-for-ssd-flash-drives/
The most important thing is getting an adapter that is compatible. The first one I bought had 30MB/s performance after purchasing the UGREEN adapter I got 300MB/s with an MX500 SATA SSD. I was pleased.
With current firmware, all I had to do was use the Raspbain installer on Windows, to install the OS on the SSD. Then boot the PI. The first boot scripts took care of setting up the SSD. Both of my PI4s have SATA SSDs.
 
Apr 24, 2021
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He also tried NVME SSDs, which maxed out at 400 megs/s roughly. Meaning the CPU was the bottleneck most probably.
So if the the entire CPU is needed to transfer data at 400mb/sec, it makes sense to cap the data rate of your storage at around 100mb/sec, to make sure that something like opening a large file doesn't swamp the entire CPU.
 

kanewolf

Titan
Moderator
But he said the CPU was "100% pegged"
OK. I never follow video links. Too much bad information on YouTube.
But, does it really matter. Either a SATA or nVME SSD has 10X the performance and lifespan of a microSD card. The downsides are cost and space. IMO, the benefits outweigh. Especially for a PI4 rather than one of the smaller form factor devices.
 
Apr 24, 2021
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But, does it really matter.
does it matter if the simple act of reading a file maxes out your CPU to 100%? Yes absolutely it does. Particularly when we're working with a RISC cpu with little in the way of multi-threading or multi-tasking optimisation. If the max the CPU can handle is 400MB/s, it makes little sense to read files that fast, since presumably you also want to do other things with your CPU than read files.

Limiting the filesystem bandwidth to 100MB/s or so (which, conveniently, happens to be how fast most mainstream MicroSD cards tend to be), means that you know that you would always have at least 75% CPU to play with, even if you were reading a file at the time.
 

kanewolf

Titan
Moderator
does it matter if the simple act of reading a file maxes out your CPU to 100%? Yes absolutely it does. Particularly when we're working with a RISC cpu with little in the way of multi-threading or multi-tasking optimisation. If the max the CPU can handle is 400MB/s, it makes little sense to read files that fast, since presumably you also want to do other things with your CPU than read files.

Limiting the filesystem bandwidth to 100MB/s or so (which, conveniently, happens to be how fast most mainstream MicroSD cards tend to be), means that you know that you would always have at least 75% CPU to play with, even if you were reading a file at the time.
You and I will just disagree.
 

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