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Date:      Tue, 26 Dec 2017 17:24:54 +0100
From:      "O. Hartmann" <ohartmann@walstatt.org>
To:        FreeBSD CURRENT <freebsd-current@freebsd.org>
Subject:   ZFS: alignment/boundary for partition type freebsd-zfs
Message-ID:  <20171226172521.611a89b0@thor.intern.walstatt.dynvpn.de>

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Running recent CURRENT on most of our lab's boxes, I was in need to replace=
 and restore a
ZFS RAIDZ pool. Doing so, I was in need to partition the disks 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 each 4 TB drive via =
the command
sequence

gpart create -s GPT adaX
gpart add -t freebsd-zfs -a 4k -l nameXX adaX

After doing this on all drives I was about to replace, something drove me t=
o check on
the net and I found a lot of websites giving "advices", how to prepare larg=
e, modern
drives for ZFS. I think the GNOP trick is not necessary any more, but many =
blogs
recommend to perform

gpart add -t freebsd-zfs -b 1m -a 4k -l nameXX adaX

to put the partition boundary at the 1 Megabytes boundary. I didn't do that=
. My
partitions all start now at block 40.

My question is: will this have severe performance consequences or is that n=
egligible?

Since most of those websites I found via "zfs freebsd alignement" are from =
years ago, I'm
a bit confused now an consideration performing all this days-taking resilve=
ring process
let me loose some more hair as the usual "fallout" ...

Thanks in advance,

Oliver

--=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).

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