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From: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
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Cc: Julien Cigar <jcigar@ulb.ac.be>, freebsd-questions@freebsd.org
Subject: Re:  Is ZFS production ready?
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>
> This is a valid argument. Checksumming is used to detect cases where the
> disk or the disk controller return invalid data to the CPU. This can happen
> for any number of reasons and isn't that unlikely. "Unrecoverable read
> error" probabilities are high enough with common drives that you can
> reasonably see them after reading 10-20TB over the course of some small
> number of years. And that's assuming no firmware bugs, no flakey cables,
> and no other of a variety of potential issues.
>

this needs scrubbing. Can be done both with ZFS and anything else.
just use dd periodically.

> I use ZFS. I like ZFS. But I also acknowledge that a zfs_fsck would be
> useful in cases where a filesystem is botched enough that it can't be

but seems you don't have any serious use for ZFS if you can take that risk 
just because you "like" ZFS.
I cannot.