alphixt
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RPi4 - MicroSD card speed classes supported?

Tue Jun 25, 2019 8:50 pm

Anyone have any idea what exactly it can support when it comes to the bottleneck?

I reviewed some of the documentation and on page 23, all that was claimed (source: https://cdn.shopify.com/s/files/1/1560/ ... y_Pi_4.pdf)
The bandwidth bottleneck to the SD card has been lifted somewhat, the data rate has been doubled. This should allow faster boot-times and applications being more snappy in general.

My questions are:
  • What is the highest UHS Speed Class supported?
  • What is the highest Video Speed Class supported?

Any additional information and documentation is greatly appreciated!

I am not only trying to sell my friends on the new RPi 4 but trying to maximize my microSD card in terms of speed. I understand that sequential and random read/write speeds vary, however, I do not want to severely over-purchase on something the board physically can not support without throttling it down heavily. I don't mind minor throttling however.

Thank you for your time in advance,
Alphixt

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Re: RPi4 - MicroSD card speed classes supported?

Tue Jun 25, 2019 11:47 pm

Welcome to the forum.

Just buy class 10 A1 rated card - anything less is not worth the savings.

Do not buy the A2 cards as the hardware in the SD card reader will not handle the electronics and reports of these being slower are t be found here and in other places.

I use SanDisk 16Gb as that’s a good balance between price and size for me BUT I normally run headless command line (i.e. Raspbian Lite) so the 16Gb is a bit OTT but plenty of space for wear levelling :D

Make sure you get them from a trusted source who will accept returns if you get issues.
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Gavinmc42
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Re: RPi4 - MicroSD card speed classes supported?

Wed Jun 26, 2019 12:06 am

I also use the Sandisc 16GB A1, I find if you shop around a little they are currently the best value.

But for the Pi4?
The 4B4 is a decent Desktop replacement, for that purpose more storage will be needed..
USB boot is still in the works but USB3 caddy for SSD will be my preferred storage.

I expect we will get some more SDcard benchmarking results for the Pi4.
So far they are showing a 600+% speed increase in USB SSD read.
How that compares to an A1 uSD?
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Andyroo
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Re: RPi4 - MicroSD card speed classes supported?

Wed Jun 26, 2019 12:10 am

You still need the SD card fir SSD boot :cry: but it knocks the socks of any SD card you can currently buy :lol:

Not in a hurry for a Pi 4 at the mo - the wallpaper has to come first :roll: (said through gritted teeth)
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echmain
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Re: RPi4 - MicroSD card speed classes supported?

Wed Jun 26, 2019 12:13 am

Andyroo wrote:
Wed Jun 26, 2019 12:10 am
You still need the SD card fir SSD boot :cry: but it knocks the socks of any SD card you can currently buy :lol:

Not in a hurry for a Pi 4 at the mo - the wallpaper has to come first :roll: (said through gritted teeth)
It's important to have a nice background image.

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alphixt
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Re: RPi4 - MicroSD card speed classes supported?

Wed Jun 26, 2019 12:15 am

Ya I personally was looking at either the Samsung MB-MC128GA/AM (128GB) or sell my soul and grab the SanDisk SDSQXPJ-128G-ANCM3 (128GB) if I could actually benefit from the read/write speeds.

  • Samsung MB-MC128GA/AM (128GB) UHS-I Read: 100MB/s, Write: 90MB/s (Sequential)
  • SanDisk SDSQXPJ-128G-ANCM3 (128GB) Read: 275 MB/s, Write: 100MB/s (Sequential)

My RPi is going to be a headless server as well. Aimed at hosting some of the projects I write that would service a few clients. The databases will not need to scale very large as of now- I just worry about read/write bottlenecks. Which is why I wanted to know the specifics when it came to what the RPi 4 would support.

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HawaiianPi
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Re: RPi4 - MicroSD card speed classes supported?

Wed Jun 26, 2019 1:31 am

alphixt wrote:
Wed Jun 26, 2019 12:15 am
Ya I personally was looking at either the Samsung MB-MC128GA/AM (128GB) or sell my soul and grab the SanDisk SDSQXPJ-128G-ANCM3 (128GB) if I could actually benefit from the read/write speeds.
You don't want either of those. Operating systems do a lot of non-sequential I/O and need high random I/O performance (IOPS).

The SanDisk Ultra A1 cards are pretty affordable and should outperform either of your choices on a Raspberry Pi. For even higher IOPS a USB 3.0 SSD would be the best performer, and in sizes of 128GB+ should not cost much more than a good A1 rated micro SD (probably cheaper than either of your original choices).

What would be interesting to know is, will (or could) the Pi4 firmware be updated to support A2 performance class cards?
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Re: RPi4 - MicroSD card speed classes supported?

Wed Jun 26, 2019 2:24 am

HawaiianPi wrote:
Wed Jun 26, 2019 1:31 am
What would be interesting to know is, will (or could) the Pi4 firmware be updated to support A2 performance class cards?
That's kind of what I am hinting at. All the documentation that I saw said that a bottleneck was slightly resolved. Still unsure what is and will be supported by the hardware. But you've help bring it to my attention that I should be looking more towards the 'A1' nomenclature (when it comes to SanDisk). I was aware of the sequential r/w not being the same as random r/w, but mistakenly believed a higher price-point card would inherently be better due to the r/w capabilities.

Thoughts on the SanDisk Ultra Plus (128GB)? Has the A1 badge and seems to be the "upgrade" to the Ultra.
Link: https://www.sandisk.com/home/memory-car ... rosd-400gb

Unfortunately, I am trying to lean away from having an external drive attached. I would like for only 2 cables extending from my RPi. Power and Ethernet. With plans on attaching the UPS Hat.

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Gavinmc42
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Re: RPi4 - MicroSD card speed classes supported?

Wed Jun 26, 2019 3:35 am

I have some USB3 tiny 32GB Lexar USB sticks I use for booting 3B+.
Will they be faster on the Pi4's when USB boot is sorted?

Will USB sticks be an alternative to SSD's?
Never had a USB3 Pi before.

At some point uSD's are more expensive than USB and SSD.
If they are not faster you are only paying for size and less reliability?
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alphixt
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Re: RPi4 - MicroSD card speed classes supported?

Wed Jun 26, 2019 3:48 am

Gavinmc42 wrote:
Wed Jun 26, 2019 3:35 am
At some point uSD's are more expensive than USB and SSD.
If they are not faster you are only paying for size and less reliability?
For what it is worth, I plan on teaming the RPi4 with the UPS Hat.

There are times where I am doing some work away from home and not near an outlet to plug the RPi into. With the RPi4 being a testing environment, the plan is to just throw it into a backpack during these moments and tethering it to my phone for a connection to SSH into. The less things I have sticking out of it, the better.

Between the WiFi, BT, and UPS hat- I'll have nothing sticking out of it and at risk of damage (like a USB stick or external SSD might.)

Main point being:
My use case isn't for everyone, which is why I worded the question to retrieve information about the Micro SD Card speed classes that are supported (A1 & A2 now included) with the Raspberry Pi 4 in particular which could be helpful information to others.

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Re: RPi4 - MicroSD card speed classes supported?

Thu Jul 11, 2019 7:05 pm

alphixt wrote:
Wed Jun 26, 2019 2:24 am

That's kind of what I am hinting at. All the documentation that I saw said that a bottleneck was slightly resolved. Still unsure what is and will be supported by the hardware.
The Pi 4 doubles the data rate at which the microSD cards can be accessed by introducing a new memory controller for them. The old memory controller (Arasan) will now drive WiFi, and the memory controller which used to drive the WiFi is now free, for custom purposes (can be accessed using the GPIO if I rememember correctly)
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alphixt
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Re: RPi4 - MicroSD card speed classes supported?

Thu Jul 11, 2019 7:18 pm

pi3g wrote:
Thu Jul 11, 2019 7:05 pm
alphixt wrote:
Wed Jun 26, 2019 2:24 am

That's kind of what I am hinting at. All the documentation that I saw said that a bottleneck was slightly resolved. Still unsure what is and will be supported by the hardware.
The Pi 4 doubles the data rate at which the microSD cards can be accessed by introducing a new memory controller for them. The old memory controller (Arasan) will now drive WiFi, and the memory controller which used to drive the WiFi is now free, for custom purposes (can be accessed using the GPIO if I rememember correctly)
I very much appreciate your insight! So from my understanding, as far as SanDisk cards go, A1 will still be supreme because the RPi 4 did not introduce additional functionality to support the A2 specification. Unfortunate news, but I am still very excited about the increased performance on such a small and cheaply priced board.

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Re: RPi4 - MicroSD card speed classes supported?

Thu Jul 11, 2019 7:37 pm

Gavinmc42 wrote:
Wed Jun 26, 2019 3:35 am
I have some USB3 tiny 32GB Lexar USB sticks I use for booting 3B+.
Will they be faster on the Pi4's when USB boot is sorted?

Will USB sticks be an alternative to SSD's?
Never had a USB3 Pi before.

At some point uSD's are more expensive than USB and SSD.
If they are not faster you are only paying for size and less reliability?
The majority of USB2.0 pendrives used to have performance roughly on par with mediocre SD cards - they had flash controllers that were not optimised for random read/random write performance. USB3.0 pendrives are generally "better" for some value of better - I would recommend getting ones that support UAS as well as USB Mass Storage, or ones that have very high sequential read speeds as this usually means they interleave reads from multiple flash chips.
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Re: RPi4 - MicroSD card speed classes supported?

Thu Jul 11, 2019 10:16 pm

If SD Express cards become more common (and cheaper), maybe the RPi4B+ could use that instead of regular SD. Is there an unused PCIe lane on the RPi4 SOC?

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Re: RPi4 - MicroSD card speed classes supported?

Thu Jul 11, 2019 11:46 pm

chipace wrote:
Thu Jul 11, 2019 10:16 pm
If SD Express cards become more common (and cheaper), maybe the RPi4B+ could use that instead of regular SD. Is there an unused PCIe lane on the RPi4 SOC?
There is only one PCIe lane, and that lane is dedicated to the USB hub.

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Re: RPi4 - MicroSD card speed classes supported?

Fri Jul 12, 2019 7:47 am

USB thumb/pen/stick drives are optimised for sequential read/write, and as such, are not the best choice for an OS drive, and certainly not a substitute for an SSD (which has very high IOPS).

I would expect most USB 3.0 stick drives to perform worse than an A1 rated SD card. SanDisk used to have a couple of models with reasonably high IOPS, but I'm pretty sure they are discontinued now, and they were quite expensive anyway.

Best bang for the buck in performance is an A1 rated micro SD card. If your storage needs are moderate, that's what I would recommend. If you need 128GB or more of storage capacity, then SSD becomes a viable option (because at those sizes they'll be roughly the same price, or possibly even cheaper than a comparable size A1 SD card).

With the old Pi 3B(+) modes there were compatibility issues when trying to boot from some USB mass storage devices, but most worked fine when booting from SD card and just using the USB drive for storage. Hopefully, with the much larger space available in the Pi4 EPROM, the boot loader will be more compatible and we won't have to deal with such issues (something to keep in mind, though).
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Re: RPi4 - MicroSD card speed classes supported?

Fri Jul 12, 2019 8:04 am

W. H. Heydt wrote:
Thu Jul 11, 2019 11:46 pm
chipace wrote:
Thu Jul 11, 2019 10:16 pm
If SD Express cards become more common (and cheaper), maybe the RPi4B+ could use that instead of regular SD. Is there an unused PCIe lane on the RPi4 SOC?
There is only one PCIe lane, and that lane is dedicated to the USB hub.
cough cough
http://mloduchowski.com/en/blog/raspber ... i-express/
from
https://hackaday.com/2019/07/10/giving- ... i-express/
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Re: RPi4 - MicroSD card speed classes supported?

Fri Jul 12, 2019 8:23 am

Looks like there has been a flash chip price drop recently.
Got a Sandisk 64GB A1 uSD and some 32GB USB 3.1 Ultra fit sticks at good prices today.

Spent about 3 times the cost of a Pi4 on memory this week.
Just got yelled at by the finance manager when the credit card bills got spotted :oops:
Might have to use loose change from now on for a while ;)

The 128GB was not too badly priced but I value my life a little bit :lol:
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