The RPI CM5…

The specs claim "ECC" [0], but give no further details. ejolson on the Raspberry Pi forums [1] thinks it is on-die ECC, not traditional ECC, which would mean transfers between the RAM and the memory controller are not protected and there is no means of monitoring errors. Some discussion on Reddit [2] also suggests it's on-die ECC. If this is true, it's better than nothing but still not a replacement for a NAS with traditional ECC RAM.

[0] https://www.raspberrypi.com/products/compute-module-5/?varia...

[1] https://forums.raspberrypi.com/viewtopic.php?p=2296449#p2296...

[2] https://old.reddit.com/r/raspberry_pi/comments/1irryax/raspb...

The chip is the memory controller…

Yes it’s on-die. Yes it has error reporting. Don’t spread fud. There isn’t a dedicated chip because there doesn’t need to be.

Broadcom BCM2712

In that case I incorrectly thought (like the other forum posters) it was like DDR5 on-die ECC. What you describe is better than DD5 on-die ECC. Is this error reporting supported by Linux? Is there some way I can do fault injection (e.g. undervolting the RAM) to check it's working?

ECC is very helpful.

Having used both, I can't help but notice how NAS' routinely run just fine without it.

>NAS' routinely run just fine without it.

How do you verify your data to confirm that?

ZFS helps, and many people are okay with the risk of a cosmic ray causing a bit flip while data is in flight once in a blue moon.

I currently manage four NASes (two primary, two backup replicas). Only one has ECC RAM. And I'm okay with my setup.

ECC is great to have, but it is oversold by some as being absolutely required for all storage devices, IMO.

For truly important files (photos), I’ll take the slight added expense of ECC for a little more peace of mind that old photos aren’t being gradually degraded with every resilver or scrub.

Good point about ZFS. Having more than one copy helps too. ECC is great when possible.

Multiple backups.

How many files have you personally seen gone corrupt on non-ecc?

ECC originated first out of server grade servers. Self-hosting rarely hits that level of demand.

My first thought is the same way everyone's laptops and desktops and cellphones without ECC data do?

I'll share any more that come to mind.

Use a RAID5 and hope the write hole doesn't eat it all =(