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Date:      Mon, 15 Feb 2016 18:28:08 -0800
From:      Freddie Cash <fjwcash@gmail.com>
To:        Paul Kraus <paul@kraus-haus.org>
Cc:        Gary Palmer <gpalmer@freebsd.org>, FreeBSD Filesystems <freebsd-fs@freebsd.org>
Subject:   Re: Hours of tiny transfers at the end of a ZFS resilver?
Message-ID:  <CAOjFWZ5GaNcw1p92XPvsneZAW1NXhaN4qBuiQeLB5U2EcUyeLg@mail.gmail.com>
In-Reply-To: <AF528DBA-CDBE-4ACB-A6FE-F5F87328EC08@kraus-haus.org>
References:  <8E04E52A-2635-4253-8140-F69495D7D0A6@panasas.com> <56C23E5B.7060207@multiplay.co.uk> <20160215213506.GB28757@in-addr.com> <AF528DBA-CDBE-4ACB-A6FE-F5F87328EC08@kraus-haus.org>

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On Feb 15, 2016 5:30 PM, "Paul Kraus" <paul@kraus-haus.org> wrote:
>
> On Feb 15, 2016, at 16:35, Gary Palmer <gpalmer@freebsd.org> wrote:
>
> > It should be noted that ZFS can do the right thing only at pool creation
> > time.  Once the pool has been created the sector size of the underlying
> > disks is baked in and can only be changed by creating a new pool on
> > the advanced format disks (or forcing the larger ashift value when
> > you initially create the pool, even if the disks are really 512 byte
> > sector drives)
>
> Is it baked in at the pool layer or the vdev layer ? I thought the ashift
was set on a vdev by vdev basis.

ashift property is set per vdev, and is set when the vdev is created. You
cab have multiple different ashift values in a single pool, although it may
be detrimental to performance.

You can see the ashift value via

"zdb poolname | grep ashift"

Cheers,
Freddie



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