A2-class microSD cards offer no better performance for the Raspberry Pi

Post by [deleted] » Mon, Jul 22, 2019, 5:46 PM UTC

geerlingguy wrote: post #38

megous wrote: post #35

A2 needs support in the Linux kernel. It's not there, yet. https://github.com/ThomasKaiser/Knowledge/blob/master/articl... "A2 promises even better performance with 4000/2000 read/write IOPS minimum but there's a problem since as outlined by the SD Association A2 cards show "much higher performance than A1 performance by using functions of Command Queuing and Cache". Cache and Command Queuing require host (driver) su…

So is there any kind of device able to use A2 cards at the rated performance yet? I can't get anything better on my Mac with multiple readers (USB 3.0 and 3.1), and I'm guessing if I tried on the reader in my 1 year old Dell XPS, I'd get the same. What good is a performance designation (A2) if no device in the real world supports it?

Post by elcritch » Mon, Jul 22, 2019, 5:53 PM UTC

jononor wrote: post #33

jws wrote: post #30

Earlier quoted context omitted.

The term you want is “microSD express”. That is the standard for PCIe and NVME on microSD cards. It specs out at about 1GB/second transfer rates. Fun engineering decisions: It can use RAM from the hosting computer to store its logical block mapping tables so it doesn’t have to have DRAM onboard for that. That’s a clever way to use what the host has in abundance to avoid putting it on the price and volume constrained…

Solder the microSD and use the solder-points for thermal connection to the board, like for most other medium-power ICs. It is also cheaper than a socket.

Post by JudgeWapner » Mon, Jul 22, 2019, 6:00 PM UTC

542458 wrote: post #52

officeplant wrote: post #16

Looks like I'll keep booting my pi's from usb attached storage. At least with the Pi4 USB speed improvements should be nice.

I didn’t even know you could do that! Any idea if it works on the pi4 or not? The docs don’t mention it. https://www.raspberrypi.org/documentation/hardware/raspberry...

Post by deepspace » Mon, Jul 22, 2019, 6:06 PM UTC

gcbw2 wrote: post #46

jokoon wrote: post #45

How about lifespan? I fail to understand why SD card have such a short lifespan, and it's the sole reason I won't acquire an RPi. It seems that the only think that is lacking on RPi is flash memory storage. Most smartphones have a lot of it, and it seems that 1GB of storage would be enough for the RPi and would not necessarily be so expensive.

smartphone batteries will go out much, much sooner than a RPi SD card write-life. And nowadays they are much harder to replace.

Post by elcritch » Mon, Jul 22, 2019, 6:22 PM UTC

mrb wrote: post #24

walrus01 wrote: post #3

The major problem is not disk write speed, which we can all agree sucks, but longevity and lifespan when used as a system boot disk and also containing /var and similar. The write wear leveling on a u3 microsd card is nowhere near as good as even a $50 consumer class ssd. Small single board computers should move towards m.2 2280 nvme drive support, or at least one sata 6 gbps interface.

There are SD cards rated for "high endurance" for example https://www.amazon.com/gp/aw/d/B07B984HJ5 is designed for continuous 24/7 writes such as surveillance cameras. These should have great longevity when used in a RPi. What I would really like to see is RPi configurations optimized to reduce writes. For example mount the whole SD card read-only, mount a few essential filesystems as ramfs (/var, /tmp, /run), and h…