eMMC vs Usb Flash on a Rock64

JSF · September 23, 2018

Trying to choose between an eMMC module or a USB Flash drive for the boot volume on a Rock64. I have a few Rock64's that I'm building as various services (Nextcloud, Pi-Hole, VPN, OMV, and/or Netatalk Backup). None of these devices will need large boot volumes as the data will be in secondary (Hard or SSD) Drives or will require VERY little data storage.

On the RPi's that the Rock64's are replacing, I've been using USB Flash drives for booting. I get the feeling that an eMMC module is a better choice, but do have any real knowledge. Are the eMMC modules more reliable and less prone to corruption that USB Flash Drives?

I do have some 32GB and 64GB eMMC models from Pine64 and am going to try them out shortly. Any thoughts and advice?

Thank you all in advance. Armbian ROCKS!

tkaiser · September 23, 2018

13 hours ago, jsfrederick said:

Are the eMMC modules more reliable and less prone to corruption that USB Flash Drives?

Depends. IMO the vast majority of problems with suddenly dying flash media (SD cards or USB pendrives) is related to fraud flash: flash memory products that fake their capacity so all of a sudden they stop working once the total amount of data written to exceeds the drive's real capacity (see here for a tool to check for this).

If you manage to buy genuine flash products (not the brands matter but where you buy -- with eBay, Aliexpress & Co. chances to get fake flash are most probably well above 50%) then there are still huge differences. Pine's cheap FORESEE eMMC modules with low capacity are way slower than the Samsung or SanDisk (Pine and other SBC vendors use for their higher capacity modules). But no idea about reliability since AFAIK all you can do here is to trust and believe since without extensive testing it's impossible to predict longevity of SD cards, eMMC and USB flash storage.

My personal take on this is

trying to minimize writes to flash storage ('Write Amplifcation' matters here, keeping stuff like logs in RAM and only write them once per hour and so on)
When using low-end flash storage preferring media that supports TRIM (that's SD cards and most probably also eMMC supporting ERASE CMD38 -- you can then TRIM them manually from time to time and maybe we get filesystem drivers in Linux that will support TRIM on (e)MMC too in the future)
Weighing eMMC with A1 rated SD cards
If huge amounts of important data need to be written to the media then always using SSDs that can be queried with SMART. The better ones provide a SMART attribute that indicates how much the storage is already worn out

Some more info:

JSF · September 23, 2018

Thanks @tkaiser, appreciate you feedback. I'll review all the links you sent and educate myself.

Luckily, other than Pi-hole, none of my use cases need to store data or logs on the flash/eMMC. I'll move everything to the hard disks. I only purchase brand name flash drives from reputable sellers like Amazon. So far, I've had NO issues with the devices I've purchased.

Thank you for all the work you do for the Armbian and SBC communities.

NicoD · September 23, 2018

Rock64 uses the same eMMC module as the Odroid's. These are among the best eMMC's. Very fast. I don't think they easily break.
They do cost a bit. And the lower capacity ones are a bit slower.
I've got 3 of them. 32GB, 64GB and 128GB. Haven't had any problem.
Thumb drives I've had much trouble with. Many die quickly. Run too hot.
As @tkaiser said. You have to look out very well not to buy crap.
But they are cheaper in lower capacity.

Make backups if you choose to use flash-drives.

Another informative link to a post of tkaiser. The C2 eMMC's are the ones for you.