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Date: Thu, 26 Mar 2020 14:07:39 +0000
From: Gary Palmer <gpalmer@freebsd.org>
To: mike tancsa <mike@sentex.net>
Cc: Attila Nagy <bra@fsn.hu>, freebsd-fs@freebsd.org
Subject: Re: Importing a vdev copied zpool from file
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On Thu, Mar 26, 2020 at 08:59:17AM -0400, mike tancsa wrote:
> On 3/25/2020 7:29 PM, Attila Nagy wrote:
> > Hi,
> >
> > I'm wondering, why this doesn't work and what could be done to make it work?
> >
> > # dd if=/dev/da0 of=/data/da0
> 
> What if you add the step
> 
> mdconfig *-o async*??-t vnode -f /data/da0
> 
> and then try the import ? Note, the async option adds a pretty big speed
> increase

At least on 11.3, that option has this caveat in the man page:

     -o [no]option
             Set or reset options.

             [no]async
                     For vnode backed devices: avoid IO_SYNC for increased
                     performance but at the risk of deadlocking the entire
                     kernel.

Not sure if the risk of deadlocking the kernel is still there or if it's
worth any potential speedup

Regards,

Gary