Re: Why is a wedge on RAID 10x slower?

[Stephen Borrill <netbsd%precedence.co.uk@localhost>]

On Thu, 5 Jan 2017, Patrick Welche wrote:
> On Wed, Nov 30, 2016 at 11:30:51AM +0000, Stephen Borrill wrote:
> > mlelstv pointed out that because of the 64 sectPerSU RAIDframe setting (i.e.
> > 128 sectors of data with 3 components, or 64k), the stripe unit is 32k, but
> > the whole stripe is 64k. By starting the wedge at 64 sectors,
> > this is 32k, but I'm attempting to do 64k I/O. Therefore the wedge should
> > start at 128, not 64
> >
> > # dkctl raid0 addwedge bigdata 128 15628073823 ffs
> > dk3 created successfully.
>
> To check: this means the bigdata wedge on raid0 has to be correctly aligned,
> but the raid0 wedge on wd0 doesn't need to be?

It would still need to be correctly aligned for the underlying sector size 
of the drive to avoid problems at the lowest level.

--
Stephen