[OmniOS-discuss] 4kn or 512e with ashift=12

[Fred Liu]

> -----Original Message-----
> From: OmniOS-discuss [mailto:omnios-discuss-bounces at lists.omniti.com] On
> Behalf Of Richard Elling
> Sent: 星期二, 三月 22, 2016 3:19
> To: Richard Jahnel
> Cc: omnios-discuss at lists.omniti.com
> Subject: Re: [OmniOS-discuss] 4kn or 512e with ashift=12
> 
> 
> > On Mar 21, 2016, at 12:00 PM, Richard Jahnel <rjahnel at ellipseinc.com>
> wrote:
> >
> > Both approaches have their error points.
> >
> > FWIW I would very very much like to be able to force my new pools into
> ashift=12. It would make drive purchasing and replacement a lot more straight
> forward and future resistant.
> 
> The fundamental problem is that this is a vdev-settable, not a pool settable.
> Today, it is very common for pools to have multiple ashifts active. Recently,
> per-vdev ZAP objects have been proposed and that code is working its way
> through the review and integration process.

Not sure how multiple-ashifts impact the performace.
> 
> Meanwhile, use one or more of the dozens of methods documented for doing
> this.
> 
> FWIW, most people with HDDs want space efficiency, because HDDs lost the
> performance race to SSDs long ago. In general, forcing everything to 4k reduces
> space efficiency, so it is unlikely to be a good default.

Agree.

Thanks.

Fred