Importing a vdev copied zpool from file

mike tancsa mike at
Thu Mar 26 14:17:34 UTC 2020

On 3/26/2020 10:07 AM, Gary Palmer wrote:
> 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

Its quite a difference in speed. I have been using it for a while on
RELENG_12 without any deadlocks while virtualizing servers.  On large
imports, it would give close to a 50% speedup


More information about the freebsd-fs mailing list