[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 Hanno Hirschberger
> Sent: 星期一, 三月 21, 2016 17:02
> To: omnios-discuss at lists.omniti.com
> Subject: Re: [OmniOS-discuss] 4kn or 512e with ashift=12
> 
> On 21.03.2016 08:00, Fred Liu wrote:
> > So that means illumos can handle 512n and 4kn automatically and properly?
> 
> Not necessarily as far as I know. Sometime drives are emulating 512 blocks and
> don't properly tell the OS about that and Illumos ZFS is aligning the drives with
> ashift=9 which leads to enormous performance issues. Also forcing the system

That is the goal(ashift=9) that 512e wants to realize. Isn't it? Emulation is to guarantee
compatiblity not performace, right?

> to handle drives with a specific sector size with the sd.conf doesn't turn out to
> be reliable in some cases (at least on my workstations). Here's what I do to

What errors have you ever seen?

> ensure ashift=12 values:
> 
> Reboot the system with a Linux live disk of your choice and install ZoL in the live
> session. Then create the ZFS pool, export it and reboot the machine. OmniOS /
> Illumos can import the new pool without problems and the ashift value is

This operation is driver-dependant. I have the similar workaround. It works for avago HBAs.
But it doesn't apply in NVMe drivers. The zpool comprised of NVMe SSDs created under ZoL can't be imported under Illumos
in my tests.

> correctly set. There was a fixed zpool binary (Solaris 11 binary) flying around the
> internet which can handle the "-o shift=12" parameter and works with OmniOS
> but unfortunately I can't find it again right now. This would make the reboot
> into a live session obsolete.
> 
> Does anyone know if the "ashift" parameter will be implemented in the OmniOS
> / Illumos zpool binary in the near future?

I think the whitelist(sd.conf) is the choice by Illumos. But we may try build it ourselves if the source is available.

Thanks.

Fred