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Date:      Thu, 27 May 2021 12:36:28 -0600
From:      Alan Somers <asomers@freebsd.org>
To:        joe mcguckin <joe@via.net>
Cc:        freebsd-fs <freebsd-fs@freebsd.org>
Subject:   Re: Upsizing a ZFS filesystem - shift question
Message-ID:  <CAOtMX2iZFMMF02OoXXThM_qqrJ6TbOWQA1wgJKS0=vZEjEr8ig@mail.gmail.com>
In-Reply-To: <BF3CEC2C-2DEB-424A-97B8-2D35FDEEFD18@via.net>
References:  <BF3CEC2C-2DEB-424A-97B8-2D35FDEEFD18@via.net>

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ashift affects how the data is laid out on disk, so you can't change it
after the drives have been replaced.  And you don't want to use ashift=3D9
for the new drives; their performance will suck.  Your best bet is to
create a new zpool, then send | receive the data from the old pool.
-Alan

On Thu, May 27, 2021 at 12:33 PM joe mcguckin <joe@via.net> wrote:

> I have an existing 32TB filesystem (2 X 8T vdevs). I want to upgrade each
> of the drives to 16TB. I pulled one drive and tried a =E2=80=98zfs replac=
e=E2=80=99 comand,
> but zfs replied with some message about new drive
> optimal ashift doesn=E2=80=99t match the vdev. It suggested Retrying  the
> =E2=80=98replace=E2=80=99 command with =E2=80=98zfs replace -o ashift=3DN=
=E2=80=99
>
> Ok, a little investigation shows the existing filesystem has an ashift of
> 9. These are older 2T drives with 512 byte sectors. The newer drives are
> 4kn sectors.
>
> Is ashift settable on a drive by drive basis? Can I temporarily set ashif=
t
> on a drive until all the drives in a vdev have been replaced?  Once all
> drives have been replaced, how do I set ashift=3D12 for all the drives in=
 the
> vdev?
>
> After replacing all the drives, will the additional space magicially
> appear or is there an additional command or series of steps?
>
> Thanks,
>
> Joe
>
> Joe McGuckin
> ViaNet Communications
>
> joe@via.net
> 650-207-0372 cell
> 650-213-1302 office
> 650-969-2124 fax
>
>
>
>

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