13 ms·

I'd agree with the hackaday commenters that this seems like they considered putting eMMC (or any kind of flash) storage on the high-end board. Would have been n

by Aissen 7y ago

I'd agree with the hackaday commenters that this seems like they considered putting eMMC (or any kind of flash) storage on the high-end board. Would have been nice considering the reliability of most microSD cards.

dividuum 7y ago
Relevant: https://www.raspberrypi.org/forums/viewtopic.php?p=1484362#p1484362 https://www.raspberrypi.org/forums/viewtopic.php?p=1484362#p...
- deleted 7y ago
  [deleted]
- ac29 7y ago
  "Nope, personal experience. SD cards have wear leveling, EMMC generally doesn't, so if using them for the same thing, the EMMC will fail first. depends on the FS." - An Engineer at Rasberry Pi. Anyone comment on that?
  - mrlambchop 7y ago
    Its an incorrect statement - I think James on the Pi forum was confusing NAND vs eMMC. eMMC has (with exception of some high grade SDCards) better write cycles and is considerably more durable than the average SDCard.
    - agildehaus 7y ago
      What about above average SD cards: the so called "industrial" SD cards?
  - imtringued 7y ago
    Average users aren't running out of write cycles. SD cards usually corrupt themselves and can be reflashed multiple times before they become physically unusable. If you are willing to pay a premium then you can get a more reliable brand but there are no guarantees that the specific model you bought is reliable. Usually corruption happens in combination with sketchy micro USB cables and power adapters (micro USB compatibility isn't actually a great benefit). Smartphones have batteries so the only thing that matters is that the average power sent to the battery exceeds the discharge rate. A temporary voltage drop for a fraction of a second can ruin the stability of your SBC and corrupt the SD card in the process. eMMC is non replaceable, therefore it has to be more resistant against power loss. Corrupting eMMC can turn the entire device into a paperweight.
    - blackflame7000 7y ago
      It 100% comes from not enough amps from a power supply. The Pi will run on less than 2000ma but at some point you are going to start getting transistor level bit flips not unlike a CPU that is overclocked too high. Things like cell phone chargers also appear to work but simply cant supply a consistent current under load because they were never designed to
akhilcacharya 7y ago
What's the write speed comparison for the Pi 4 and an equivalent SBC with eMMC? I'm very tempted to buy one for general purpose compute but I'm wondering if I should get the RockPro instead (inferior software support but theoretically superior performance).
- Fronzie 7y ago
  I've had Odroid devices in the past. Although they by all means work as advertised, the SW support for the raspberry pi is higher, allowing more recent kernels and with more (most) of the sources available also more tinkering. I'd recommend to settle for the lower performance unless you really really need it.
- opencl 7y ago
  The SD controller has been improved somewhat from the older Pi models, this article has some storage benchmarks: https://www.cnx-software.com/2019/06/24/raspberry-pi-4-benchmarks-mini-review/ https://www.cnx-software.com/2019/06/24/raspberry-pi-4-bench... Odroid has some eMMC performance numbers: https://magazine.odroid.com/article/orange-emmc-module-samsung-5-1-chipset-arrives/ https://magazine.odroid.com/article/orange-emmc-module-samsu... Though on either board the fastest storage you'll get will likely be a USB3->SATA bridge with an SSD.
mrlambchop 7y ago
A major product challenge of eMMC in a design is the requirement to supply a means of flashing data onto the storage device when the CPU can't boot from the eMMC (or the disk is corrupted). The SDCard solves this problem fairly well (although the solution requires a reasonable level of computer literacy due to the filesystems and raw block device access needed, however its a good fit for the Pi user demographic). Other systems solve this chicken/egg problem by having a tool that runs on a PC that can perform the programming of attached storage, often by downloading code and data into a CPUs RAM and then having it flash to the disk. Exposing JTAG to Pi customers however is a step too far and would require more expensive external JTAG hardware to be needed per customer as well. If I was Pi, I'd put a 10cent USB stick IC onto the board that connects in parallel to the eMMC and enable the board to be plugged into any USB host and mounted as external storage. Some programmable logic (get one of the Silego 10cent programmable logic ICs) would be needed to prevent the USB from being mounted when the system was running - I'd probably add in a button or switch that is read at power on and determines which interface gets to see the eMMC. It would need to hold either the Pi chip or the USB IC in reset depending on which function was selected. A second option would be to put an USB eMMC protocol stack into the BootROM, but this would need LittleKernel or something similar in the BootROM and its non-trivial to get right!
- pedrocx486 7y ago
  They could go the "Android way" and have a fastboot of sorts to boot software like a recovery OS to reflash the main os.
  - mrlambchop 7y ago
    I believe fast boot relies on having a stable, on PCB storage device (eMMC or NAND) to ensure that the recovery method doesn't have any opportunity to get wiped / trashed. Using an SDCard doesn't ensure this and thus something in hardware would be needed instead.
realshowbiz 7y ago
Ive been running raspberry pis on sd cards for years and really haven't had any issues. And if I did have an issue I’d just fire up a new sd card and dd the disk image back on. It’s actually one of the great features of the PI IMO, having the ability to quickly swap disks and reboot. Reminds me of the computers and video games of yesterday.
- blackflame7000 7y ago
  I agree, as long as you store everything permanent on a centralized database then being able to fix a node in a cluster is just a card swap.
giobox 7y ago
This! When I saw a new Pi was announced with multiple models I dearly hoped for one with optional reliable on board storage. The MicroSD card is easy to use, but just not remotely close to reliable enough as the only kind of onboard storage for many use cases. I migrated a few years ago to the ASU’s Up! Board - same dimensions, GPIO, general layout as a Pi but with quad core atom, 32GB onboard storage, 4gb of ram and “proper” gigabit Ethernet. No more micro SD card failures (I’m aware usb and network boot exist for the Pi but does not fit my needs). This Pi 4 ticks all of those boxes except for the storage. So close to a truly great little home server device.

by Aissen 7y ago

dividuum 7y ago

Relevant: https://www.raspberrypi.org/forums/viewtopic.php?p=1484362#p1484362 https://www.raspberrypi.org/forums/viewtopic.php?p=1484362#p...

deleted 7y ago
[deleted]
ac29 7y ago
"Nope, personal experience. SD cards have wear leveling, EMMC generally doesn't, so if using them for the same thing, the EMMC will fail first. depends on the FS." - An Engineer at Rasberry Pi. Anyone comment on that?
- mrlambchop 7y ago
  Its an incorrect statement - I think James on the Pi forum was confusing NAND vs eMMC. eMMC has (with exception of some high grade SDCards) better write cycles and is considerably more durable than the average SDCard.
  - agildehaus 7y ago
    What about above average SD cards: the so called "industrial" SD cards?
- imtringued 7y ago
  Average users aren't running out of write cycles. SD cards usually corrupt themselves and can be reflashed multiple times before they become physically unusable. If you are willing to pay a premium then you can get a more reliable brand but there are no guarantees that the specific model you bought is reliable. Usually corruption happens in combination with sketchy micro USB cables and power adapters (micro USB compatibility isn't actually a great benefit). Smartphones have batteries so the only thing that matters is that the average power sent to the battery exceeds the discharge rate. A temporary voltage drop for a fraction of a second can ruin the stability of your SBC and corrupt the SD card in the process. eMMC is non replaceable, therefore it has to be more resistant against power loss. Corrupting eMMC can turn the entire device into a paperweight.
  - blackflame7000 7y ago
    It 100% comes from not enough amps from a power supply. The Pi will run on less than 2000ma but at some point you are going to start getting transistor level bit flips not unlike a CPU that is overclocked too high. Things like cell phone chargers also appear to work but simply cant supply a consistent current under load because they were never designed to

akhilcacharya 7y ago

What's the write speed comparison for the Pi 4 and an equivalent SBC with eMMC? I'm very tempted to buy one for general purpose compute but I'm wondering if I should get the RockPro instead (inferior software support but theoretically superior performance).

Fronzie 7y ago
I've had Odroid devices in the past. Although they by all means work as advertised, the SW support for the raspberry pi is higher, allowing more recent kernels and with more (most) of the sources available also more tinkering. I'd recommend to settle for the lower performance unless you really really need it.
opencl 7y ago
The SD controller has been improved somewhat from the older Pi models, this article has some storage benchmarks: https://www.cnx-software.com/2019/06/24/raspberry-pi-4-benchmarks-mini-review/ https://www.cnx-software.com/2019/06/24/raspberry-pi-4-bench... Odroid has some eMMC performance numbers: https://magazine.odroid.com/article/orange-emmc-module-samsung-5-1-chipset-arrives/ https://magazine.odroid.com/article/orange-emmc-module-samsu... Though on either board the fastest storage you'll get will likely be a USB3->SATA bridge with an SSD.

mrlambchop 7y ago

A major product challenge of eMMC in a design is the requirement to supply a means of flashing data onto the storage device when the CPU can't boot from the eMMC (or the disk is corrupted). The SDCard solves this problem fairly well (although the solution requires a reasonable level of computer literacy due to the filesystems and raw block device access needed, however its a good fit for the Pi user demographic). Other systems solve this chicken/egg problem by having a tool that runs on a PC that can perform the programming of attached storage, often by downloading code and data into a CPUs RAM and then having it flash to the disk. Exposing JTAG to Pi customers however is a step too far and would require more expensive external JTAG hardware to be needed per customer as well. If I was Pi, I'd put a 10cent USB stick IC onto the board that connects in parallel to the eMMC and enable the board to be plugged into any USB host and mounted as external storage. Some programmable logic (get one of the Silego 10cent programmable logic ICs) would be needed to prevent the USB from being mounted when the system was running - I'd probably add in a button or switch that is read at power on and determines which interface gets to see the eMMC. It would need to hold either the Pi chip or the USB IC in reset depending on which function was selected. A second option would be to put an USB eMMC protocol stack into the BootROM, but this would need LittleKernel or something similar in the BootROM and its non-trivial to get right!

pedrocx486 7y ago
They could go the "Android way" and have a fastboot of sorts to boot software like a recovery OS to reflash the main os.
- mrlambchop 7y ago
  I believe fast boot relies on having a stable, on PCB storage device (eMMC or NAND) to ensure that the recovery method doesn't have any opportunity to get wiped / trashed. Using an SDCard doesn't ensure this and thus something in hardware would be needed instead.

realshowbiz 7y ago

Ive been running raspberry pis on sd cards for years and really haven't had any issues. And if I did have an issue I’d just fire up a new sd card and dd the disk image back on. It’s actually one of the great features of the PI IMO, having the ability to quickly swap disks and reboot. Reminds me of the computers and video games of yesterday.

blackflame7000 7y ago
I agree, as long as you store everything permanent on a centralized database then being able to fix a node in a cluster is just a card swap.

giobox 7y ago

This! When I saw a new Pi was announced with multiple models I dearly hoped for one with optional reliable on board storage. The MicroSD card is easy to use, but just not remotely close to reliable enough as the only kind of onboard storage for many use cases. I migrated a few years ago to the ASU’s Up! Board - same dimensions, GPIO, general layout as a Pi but with quad core atom, 32GB onboard storage, 4gb of ram and “proper” gigabit Ethernet. No more micro SD card failures (I’m aware usb and network boot exist for the Pi but does not fit my needs). This Pi 4 ticks all of those boxes except for the storage. So close to a truly great little home server device.