have you ever successfully broken the zfs to the point where it’s not recoverable?
Mirror vdevs are the only way to go. Accept the 50% and sleep at night.
that’s no fun. also, it turned out that this is not a disk error, the zfs metadata got corrupted and now I get a panic when trying to mount this.
ZFS is very thoughtful and paranoid so it shouldn’t just corrupt. You probably have a silent hardware failure
Trying to import my pool causes a panic, so maybe? Though am still in the middle of trying to recover, just haven’t had time to work on it yet.
I’ve had this, with a single disk pool.
Copies = 2 might have saved you
my achievement here is that this is a proper raidz setup with multiple disks and ecc ram
Raidz1 or z2? One of the reasons I went with z2 is because of the “raid5 is dead” thing, argument basically being, drives are so large that if 1 fails, you are statistically almost guaranteed to encounter a read error during the rebuild when you no longer have any redundancy, so double redundancy is a necessity nowadays.
I have a raidz5 array of 8tb drives, one died, replaced it with no issues
Raidz5 doesn’t exist, I assume you mean raid5? And you wouldn’t know, URE is sometimes silent, and because without parity during a rebuild you would be recalculating the parity bit and assumig every read on the remaining drives is successful. Except the URE rate for drives hasn’t gone down to match the increasing size of drives - so for a full 1x read of a large drive, you’re statistically at risk to get at least 1 URE.
In short, there is no integrity checking when rebuilding a single redundancy array after a drive failure, so just because a rebuild succeeds, doesn’t mean nothing was lost or corrupted. With double redundancy, you will still have single redundancy during a rebuild, so you would be able to detect URE and retry reads or raise an error to the user.
Some articles may make it overblown - you won’t lose your whole array, but any files stored in the block that had the URE during rebuild would be lost. And you might not know that it happened.
You can read about it here: https://www.servnetuk.com/insights/ure-is-raid-5-dead
oof
