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

Post by fragmede » Mon, Jul 22, 2019, 11:39 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 zamadatix » Mon, Jul 22, 2019, 11:55 PM UTC

djsumdog wrote: post #18

I'm surprised we haven't seen a smaller than M.2 form factor for SATA on embedded devices. It seems like the big limiter on devices like the Raspberry Pi and others are the sd cards/emmc modules, since the amount processing power and ram have been continually going up. If you need disk performance on the Pi 4, wouldn't it make more sense to only keep the kernel,initrd on the sdcard and mount the primary filesystem of…

Post by rnantes » Tue, Jul 23, 2019, 12:14 AM UTC

geerlingguy wrote: post #25

jdietrich wrote: post #20

Earlier quoted context omitted.

The SD 7.0 standard includes support for PCIe and NVMe. https://www.sdcard.org/press/SD_EXPRESS_A_REVOLUTIONARY_INNO...

Good chance that doesn't trickle down to the microSD interface; it seems like the best performance improvements are reserved for the full-size SD cards, likely because they can fit more thermal mass and connection pins in the larger case.

Post by sebcat » Tue, Jul 23, 2019, 1:19 AM UTC

jononor wrote: post #34

jononor wrote: post #32

Earlier quoted context omitted.

General practice in embedded is to avoid writing to disk as much as possible. Data collection is mostly done by sending it to the cloud for storage there. However 'edge processing' and 'edge storage' are hot topics, so there will probably be more work in this area. Some of the surveillance camera vendors are showing interest in this, since it would be beneficial to reduce data needed to be sent. Especially since vast…

Many embedded applications are also not particularly form-factor constrained. A good security camera lens is often easily bigger than a couple of 2.5" hard-drives and a medium sized single-board computation. Heck, just wiring boxes for an industrial sensor system, are can often bigger than 10s of 3.5" disks.

Post by whenchamenia » Tue, Jul 23, 2019, 2:23 AM UTC

cptskippy wrote: post #100

ripdog wrote: post #96

Earlier quoted context omitted.

The UK has to do that because the fastest widely-deployed internet connections available are VDSL2. DSL connections in general are relatively unreliable, and speeds vary wildly depending on a variety of factors, most importantly the length of the cable between you and your cabinet/exchange. Australian folks may chime in here with tales of their DSL connections dropping out during heavy rain, when their telephone junc…

On the flip side, in the early 2000s Bellsouth (now AT&T) deployed FTTP in much of the Southeast and would convert that to ADSL to plug into existing house POTS wiring. It was sold as ADSL at 12mb/s. There was literally no other internet option available from them at the time either.