Raspberry Pi Forums

SAMSUNG 32GB FIT USB 3.0
Did anyone managed to boot from this stick successfully?
I'm trying to find a 16GB/32GB USB 3.0 stick to boot the OS from it (hopefully for much faster I/O speed ).

pror21 wrote:SAMSUNG 16GB FIT USB 3.0
Did anyone managed to boot from this stick?
I'm trying to find a 16GB/32GB USB 3.0 stick to boot the OS from it (hopefully for much faster I/O speed ).

Only the Raspberry Pi 3B can boot from USB Mass Storage Device and like all Raspberry Pi's only has a USB 2.0 BUS so are limited to that I/O speed.

In the Raspberry Pi Blog a few devices were noted as verified working: https://www.raspberrypi.org/blog/pi-3-b ... orage-boot

You can boot from the microSD card then, as part of the boot, switch to a USB device. You only need a tiny microSD card for the first part of the boot. A config file redirects the boot. There are descriptions under "using an SSD".

USB is limited to 35 MB/s for disk access. Cheap cards have read speeds about 20 MB/s. Middle priced cards reach 40 MB/s, fore than you need for reads.

Fast cards and fast USB sticks make a difference for random writes, the slowest activity on flash memory. Expensive cards and medium priced sticks often drop back to 10 MB/s or less. A fast USB device might make a huge difference to something like a database update.

I purchased the absolute fastest microSD card for a test Web server. The card has random write speeds slightly faster than USB 2. The super fast microSD card was chosen purely for fast database updates.

But the OS is working most of the time with random read/writes too. That is why i wan't to use a USB stick.
If i understood correctly, you said Raspberry PI 3 USB 3.0 is limited to 35MB/s. Why is that? Is it because of the slow controller / bus?

pror21 wrote:But the OS is working most of the time with random read/writes too. That is why i wan't to use a USB stick.
If i understood correctly, you said Raspberry PI 3 USB 3.0 is limited to 35MB/s. Why is that? Is it because of the slow controller / bus?

Am Raspberry Pi,s as I stated are USB 2.0:

http://www.mikronauts.com/raspberry-pi/ ... ment-howto

This also applies to the 3B

fruitoftheloom wrote:

pror21 wrote:But the OS is working most of the time with random read/writes too. That is why i wan't to use a USB stick.
If i understood correctly, you said Raspberry PI 3 USB 3.0 is limited to 35MB/s. Why is that? Is it because of the slow controller / bus?

Am Raspberry Pi,s as I stated are USB 2.0:

http://www.mikronauts.com/raspberry-pi/ ... ment-howto

This also applies to the 3B

Oh.. okay. Although it seems quite good speed especially for random read/writes, USB 2.0 specification is 480Mbits/s (60MB/s). I guess that is just a theoretical max speed.

Btw it would be very helpful if someone could give me a random read/write benchmark on a USB stick that is done of course from a Raspberry Pi 3B.

pror21 wrote:

fruitoftheloom wrote:

pror21 wrote:But the OS is working most of the time with random read/writes too. That is why i wan't to use a USB stick.
If i understood correctly, you said Raspberry PI 3 USB 3.0 is limited to 35MB/s. Why is that? Is it because of the slow controller / bus?

Am Raspberry Pi,s as I stated are USB 2.0:

http://www.mikronauts.com/raspberry-pi/ ... ment-howto

This also applies to the 3B

Oh.. okay. Although it seems quite good speed especially for random read/writes, USB 2.0 specification is 480Mbits/s (60MB/s). I guess that is just a theoretical max speed.

Btw it would be very helpful if someone could give me a random read/write benchmark on a USB stick that is done of course from a Raspberry Pi 3B.

The USB BUS is exactly the same on the 3B as it was on a 2B, why do you think it should be different ??

Nothing, i just forgot to type that . So even from a 2B a benchmark would be very helpful.

I put a very fast device in a Pi 3 and had read/write speeds hovering around 36 MB/s with occasional 37 MB/s. On USB 3, the device speed is triple that. The 36 MB/s is the Pi 3 maximum speed.

10% of USB 2 bandwidth is reserved for keyboard, mouse, etc. With overheads, a byte uses about 10 bits. 480 megabits becomes 48 megabytes. Take out 5 MB/s for the keyboard reserve, you get 43. Take out another 10% for the file copy overhead, you get 38 MB/s. When copying large files, the speed approaches 38 MB/s.

https://petermoulding.com/raspberry-pi/ ... rtup-speed
Benchmark copying from very fast SSD, 200 MB/s, to very fast microSD card with 80 MB/s write speed. Produced less than USB 2 transfer speed.