6 ms·

If ZFS is anything like BTRFS, then I don't think ECC is super necessary. Yeah, it'll prevent problem from eventually cropping up when the RAM shits itself, but

If ZFS is anything like BTRFS, then I don't think ECC is super necessary. Yeah, it'll prevent problem from eventually cropping up when the RAM shits itself, but it's not like those issues compound silently in the night. When my ram started going a bit down the drain, (Flipping the occasional bit. Rare enough that the system still ran fine) I was hounded with checksum errors and any attempt to work with the data was met with error messages until I got new RAM. I don't think ECC is really all that important unless you're dealing with data worth thousands of dollars or more.

guitarbill 10y ago
IDK, I've seen some odd RAM failure modes where the base OS would run fine, but then depending on the load (e.g. games) some weird stuff would happen like a BSOD after exactly <x> minutes of gameplay. Once ZFS writes corrupted metadata with corrupted checksums to the disk, it's very hard to recover that data. Yes, ZFS is not backup, but the implications of serving clients messed up data is also worrying in certain business cases. Given that ECC RAM isn't (much?) more expensive, why not just use ECC? (For my microserver I remember it being the same price as non-ECC.) Well, because CPUs with ECC support are rare, etc.
- boomboomsubban 10y ago
  The RAM itself isn't much more expensive, it's a compatible motherboard and CPU that add to the price. If you can't afford even a temporary loss of data it's well worth the cost. That is true with whatever filesystem you choose, and ZFS is always a great choice.
- mioelnir 10y ago
  Once any filesystem writes data that was corrupted in memory, the data is hard to recover. And any filesystem will serve this corrupted data if asked, since it is all that it has. This is not a ZFS specific failure mode. Without ECC, ZFS loses one of the guarantees that it otherwise provides. But it only degrades down to how bad every filesystem is in the face of memory corruption - not worse.

guitarbill 10y ago

IDK, I've seen some odd RAM failure modes where the base OS would run fine, but then depending on the load (e.g. games) some weird stuff would happen like a BSOD after exactly <x> minutes of gameplay. Once ZFS writes corrupted metadata with corrupted checksums to the disk, it's very hard to recover that data. Yes, ZFS is not backup, but the implications of serving clients messed up data is also worrying in certain business cases. Given that ECC RAM isn't (much?) more expensive, why not just use ECC? (For my microserver I remember it being the same price as non-ECC.) Well, because CPUs with ECC support are rare, etc.

boomboomsubban 10y ago
The RAM itself isn't much more expensive, it's a compatible motherboard and CPU that add to the price. If you can't afford even a temporary loss of data it's well worth the cost. That is true with whatever filesystem you choose, and ZFS is always a great choice.
mioelnir 10y ago
Once any filesystem writes data that was corrupted in memory, the data is hard to recover. And any filesystem will serve this corrupted data if asked, since it is all that it has. This is not a ZFS specific failure mode. Without ECC, ZFS loses one of the guarantees that it otherwise provides. But it only degrades down to how bad every filesystem is in the face of memory corruption - not worse.