Skip site navigation (1)Skip section navigation (2)
Date:      Tue, 26 Dec 2017 18:04:44 +0100
From:      "O. Hartmann" <ohartmann@walstatt.org>
To:        Allan Jude <allanjude@freebsd.org>
Cc:        freebsd-current@freebsd.org
Subject:   Re: ZFS: alignment/boundary for partition type freebsd-zfs
Message-ID:  <20171226180511.4d7d422e@thor.intern.walstatt.dynvpn.de>
In-Reply-To: <bf2738b0-1774-af26-fd1e-151b6bd66c52@freebsd.org>
References:  <20171226172521.611a89b0@thor.intern.walstatt.dynvpn.de> <bf2738b0-1774-af26-fd1e-151b6bd66c52@freebsd.org>

next in thread | previous in thread | raw e-mail | index | archive | help
--Sig_/GflVNx9FQAYEcP..BDCX8zP
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

Am Tue, 26 Dec 2017 11:44:29 -0500
Allan Jude <allanjude@freebsd.org> schrieb:

> On 2017-12-26 11:24, O. Hartmann wrote:
> > Running recent CURRENT on most of our lab's boxes, I was in need to rep=
lace and
> > restore a ZFS RAIDZ pool. Doing so, I was in need to partition the disk=
s I was about
> > to replace. Well, the drives in question are 4k block size drives with =
512b emulation
> > - as most of them today. I've created the only and sole partiton on eac=
h 4 TB drive
> > via the command sequence
> >=20
> > gpart create -s GPT adaX
> > gpart add -t freebsd-zfs -a 4k -l nameXX adaX
> >=20
> > After doing this on all drives I was about to replace, something drove =
me to check on
> > the net and I found a lot of websites giving "advices", how to prepare =
large, modern
> > drives for ZFS. I think the GNOP trick is not necessary any more, but m=
any blogs
> > recommend to perform
> >=20
> > gpart add -t freebsd-zfs -b 1m -a 4k -l nameXX adaX
> >=20
> > to put the partition boundary at the 1 Megabytes boundary. I didn't do =
that. My
> > partitions all start now at block 40.
> >=20
> > My question is: will this have severe performance consequences or is th=
at negligible?
> >=20
> > Since most of those websites I found via "zfs freebsd alignement" are f=
rom years ago,
> > I'm a bit confused now an consideration performing all this days-taking=
 resilvering
> > process let me loose some more hair as the usual "fallout" ...
> >=20
> > Thanks in advance,
> >=20
> > Oliver
> >  =20
>=20
> The 1mb alignment is not required. It is just what I do to leave room
> for the other partition types before the ZFS partition.
>=20
> However, the replacement for the GNOP hack, is separate. In addition to
> aligning the partitions to 4k, you have to tell ZFS that the drive is 4k:
>=20
> sysctl vfs.zfs.min_auto_ashift=3D12
>=20
> (2^12 =3D 4096)
>=20
> Before you create the pool, or add additional vdevs.
>=20

I didn't do the sysctl vfs.zfs.min_auto_ashift=3D12 :-(( when I created the=
 vdev. What is
the consequence for that for the pool? I lived under the impression that th=
is is necessary
for "native 4k" drives.

How can I check what ashift is in effect for a specific vdev?

--=20
O. Hartmann

Ich widerspreche der Nutzung oder =C3=9Cbermittlung meiner Daten f=C3=BCr
Werbezwecke oder f=C3=BCr die Markt- oder Meinungsforschung (=C2=A7 28 Abs.=
 4 BDSG).

--Sig_/GflVNx9FQAYEcP..BDCX8zP
Content-Type: application/pgp-signature
Content-Description: OpenPGP digital signature

-----BEGIN PGP SIGNATURE-----

iLUEARMKAB0WIQQZVZMzAtwC2T/86TrS528fyFhYlAUCWkKBRwAKCRDS528fyFhY
lNE/AgCP/mI7TEfhdTPDYjVAny5DGWXylgPb4BpzzPcYSWBOAg+2nIdT9ySrwIq2
pLtsY9iAUqb9mmNDEVnn7LAkSQ0DAf9OdpNlKh+bcU8SAsmxNflih9NScl8djrdb
7Hsc1MFS1crG8Wwvwv8KFpZnfcPAyB6AjV3M4hKYNb+DwduO61Fu
=gHOZ
-----END PGP SIGNATURE-----

--Sig_/GflVNx9FQAYEcP..BDCX8zP--



Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20171226180511.4d7d422e>