[OpenIndiana-discuss] vdev reliability was: Recommendations for fast storage

[Edward Ned Harvey (openindiana)]

> From: Sebastian Gabler [mailto:sequoiamobil at gmx.net]
> 
> AFAIK, a bit error in Parity or stripe data can be specifically
> dangerous when it is raised during resilvering, and there is only one
> layer of redundancy left. 

You're saying "error in parity," but that's because you're thinking of raidz, which I don't usually use.  You really mean "error in redundant copy," and the only risk, as you've identified, is the error in the *last* redundant copy.

The answer to this is:  You *do* scrub every week or two, don't you?    You should.


> I do not think that zfs will have better resilience against rot of
> parity data than conventional RAID.

That's incorrect, because conventional raid cannot scrub proactively.

Sure, if you have a pool with only one level of redundancy, and the bit error creeped in between the most recent scrub and the present failure time, then that's a problem, and zfs cannot protect you against it.  This is, by definition, simultaneous failure of all redundant copies of the data.