Hi Austin,

I’m not trying to change the ashift of a pool, I’m trying to override the 
physical block size of a new 4k-sector sized device so I can attach it to an 
existing ashift=9 zpool.

Perhaps I’m doing it backwards trying to add a 4k sector drive to a 512b sector 
pool, and the override only works the other way?

If that’s the case, I’m happy to zfs send to a new ashift=12 pool.

-Matt.

On 16 Mar 2014, at 12:33 pm, Austin Wise <[email protected]> wrote:

> Hi Matt,
> 
> The ashift is a property of vdevs at the top of the configuration tree.  It 
> is not of a property of the vdevs below mirrors and raidz vdevs.  So 
> replacing a drive in a mirror or raidz vdev won't affect this property.
> 
> I also have a suspicion that you can't change the ashift without recreating 
> the pool.  A spacemap with a larger ashift would not be able to describe the 
> closely packed allocations in a vdev with a smaller ashift.  So increasing 
> the ashift would require rewriting all the blocks and block pointers to fit 
> in the coarser allocation granularity.  I don't believe this block pointer 
> rewrite code exists yet.
> 
> Regards,
> Austin
> 
> 
> 
> On Sat, Mar 15, 2014 at 2:53 PM, Matt Connolly <[email protected]> wrote:
> Dear list,
> 
> I’ve just replaced a drive in a zpool with ashift=9 with a new drive that has 
> 4k sectors.
> 
> I’ve read through several instructional pages and I cannot override the size 
> by editing the /kernel/drv/sd.conf file, according to:
> 
> http://wiki.illumos.org/display/illumos/ZFS+and+Advanced+Format+disks
> http://blog.delphix.com/gwilson/2012/11/15/4k-sectors-and-zfs/
> 
> Is the following feature included in the SmartOS live kernel?
> 
> https://www.illumos.org/issues/2665
> 
> Perhaps it is and it only supports making block sizes larger, not smaller?
> 
> 
> Thanks
> Matt
> 
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