ZFS and mdconfig -t vnode - Unexpected behavior

[Tom Evans]

On Thu, Mar 8, 2012 at 4:19 PM, Dan Rue <drue at therub.org> wrote:
> I have discovered an unexpected behavior when using ZFS against a vnode.
> When running mdconfig -d against a vnode, there is a long delay before
> the blocks are fully written to the backing store file. Consider the
> following test script:
>
> […]
>
> Are there any ZFS tunables that could be related to this? What could be
> the cause of this behavior?
>

The tunable vfs.zfs.txg.timeout (in seconds) controls how bursty ZFS
is. I run with a high value (30), so my disks don't get constantly
hit, but if you lowered it, data will be written much more frequently.

Cheers

Tom