gmirror + ZFS issues

[Karl Denninger]

On 5/16/2014 8:23 AM, Nicolas Haller wrote:
> Hello,
>
> I've got a new server and I installed FreeBSD 10 on it. I have a 
> problem to create a new zfs pool. The command stalls on IO wait (D 
> state / zio->io_cv).
>
> The device for the pool is a 1.7T partition (index 4) of a gmirror 
> device.
Why?

ZFS provides its own mirroring and it is superior, as it checksums each 
block and thus does not rely on the drive returning an error to detect 
problems.  It can also rewrite a bad block (assuming the problem is 
transient) and scrub also relies on independent components.

You're destroying the data integrity advantage that ZFS gives you by 
using a gmirror under it.  Stop doing that and see if your problem 
disappears.

(In other words it sounds like the problem is real but you shouldn't be 
doing that anyway, so it also shouldn't bite you.)

-- 
-- Karl
karl at denninger.net


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