[OmniOS-discuss] mixing 512B and 4K disks in vdev

[Michael Rasmussen]

On Thu, 19 Nov 2015 13:55:50 -0500
Chris Siebenmann <cks at cs.toronto.edu> wrote:

> > I have to replace a HDD disk in a mirrored vdev which is using
> > ashift=9.  The problem is that all new HDD's is 4K disks so I wonder
> > if anyone has made some performance measurements of using a 4K disk
> > with ashift=9 in contrast to the obvious ashift=12?
> >
> > As I understand it you cannot detach a vdev from a pool so it is not
> > possible to replace both disks with 4K disks. How do you handle a
> > situation like this?  
> 
>  OmniOS will not normally allow you to add a 4k disk to a vdev with
> ashift=9, regardless of any performance impact. As far as I know, in
> order to get around this you must modify /kernel/drv/sd.conf in order
> to lie about the disk's physical sector size, per:
If the disk is a 512e type this is possible. Meaning 512B is reported
to the kernel and the driver firmware will handle converting to 4K.

> 
>  If you can't run 4k disks this way (or don't want to), as far as I know
> your only option is to create an entire new pool with new vdevs that are
> all ashift=12.
> 
somewhat frustrating that a solution for transitioning a 512B vdev to
4K apart from creating a new pool has not be made.

-- 
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Michael Rasmussen

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