[lgg]

That is ABSOLUTELY incorrect. SSDs have enormous amounts of error detection and correction builtin explicitly because errors on the raw medium are so common that without it you would never be able to read correct data from the device.

It has been years since I was familiar enough with the insides of SSDs to tell you exactly what they are doing now, but even ~10-15 years ago it was normal for each raw 2k block to actually be ~2176+ bytes and use at least 128 bytes for LDPC codes. Since then the block sizes have gone up (which reduces the number of bytes you need to achieve equivalent protection) and the lithography has shrunk (which increases the raw error rate).

Where exactly the error correction is implemented (individual dies, SSD controller, etc) and how it is reported can vary depending on the application, but I can say with assurance that there is no chance your OS sees uncorrected bits from your flash dies.

[zie]

> I can say with assurance that there is no chance your OS sees uncorrected bits from your flash dies.

While true, there is zero promises that what you meant to save and what gets saved are the same things. All the drive mostly promises is that if the drive safely wrote XYZ to the disk and you come back later, you should expect to get XYZ back.

There are lots of weasel words there on purpose. There is generally zero guarantee in reality and drives lie all the time about data being safely written to disk, even if it wasn't actually safely written to disk yet. This means on power failure/interruption the outcome of being able to read XYZ back is 100% unknown. Drive Manufacturers make zero promises here.

On most consumer compute, there is no promises or guarantees that what you wrote on day 1 will be there on day 2+. It mostly works, and the chances are better than even that your data will be mostly safe on day 2+, but there is zero promises or guarantees. We know how to guarantee it, we just don't bother(usually).

You can buy laptops and desktops with ECC RAM and use ZFS(or other checksumming FS), but basically nobody does. I'm not aware of any mobile phones that offer either option.

[crazygringo]

> While true, there is zero promises that what you meant to save and what gets saved are the same things. All the drive mostly promises is that if the drive safely wrote XYZ to the disk and you come back later, you should expect to get XYZ back.

I'm not really sure what point you're trying to make. It's using ECC, so they should be the same bytes.

There isn't infinite reliability, but nothing has infinite reliability. File checksums don't provide infinite reliability either, because the checksum itself can be corrupted.

You keep talking about promises and guarantees, but there aren't any. All there is are statistical rates of reliability. Even ECC RAM or file checksums don't offer perfect guarantees.

For daily consumer use, the level of ECC built into disks is generally plenty sufficient. It's chosen to be so.

[zie]

I would disagree that disks alone are good enough for daily consumer use. I see corruption often enough to be annoying with consumer grade hardware without ECC & ZFS. Small images are where people usually notice. They tend to be heavily compressed and small in size means minor changes can be more noticeable. In larger files, corruption tends to not get noticed as much in my experience.

We have 10k+ consumer devices at work and corruption is not exactly common, but it's not rare either. A few cases a year are usually identified at the helpdesk level. It seems to be going down over time, since hardware is getting more reliable, we have a strong replacement program and most people don't store stuff locally anymore. Our shared network drives all live on machines with ECC & ZFS.

We had a cloud provider recently move some VM's to new hardware for us, the ones with ZFS filesystems noticed corruption, the ones with ext4/NTFS/etc filesystems didn't notice any corruption. We made the provider move them all again, the second time around ZFS came up clean. Without ZFS we would have never known, as none of the EXT4/NTFS FS's complained at all. Who knows if all the ext4/NTFS machines were corruption free, it's anyone's guess.