Date: Fri, 11 Sep 2015 10:27:11 -0500 From: Graham Allan <allan@physics.umn.edu> To: freebsd-questions@freebsd.org Subject: Re: followup storage question Message-ID: <55F2F2CF.3080004@physics.umn.edu> In-Reply-To: <55F2D086.6060509@hiwaay.net> References: <55F2D086.6060509@hiwaay.net>
next in thread | previous in thread | raw e-mail | index | archive | help
On 9/11/2015 7:59 AM, William A. Mahaffey III wrote: > > > The Wiki page https://wiki.freebsd.org/RootOnZFS/GPTZFSBoot/9.0-RELEASE > illustrates using gnop to enforce 4K alignment of gpt partitions for > subsequent use by ZFS. However the gpart commands also use the '-a 4k' > arguments, aligning partitions on 4k boundaries as I understand things. > Is the gnop command also necessary ? TIA & have a nice weekend. My experience is I only ever install on smaller devices so never really worry about 4k alignment at that time, only for making large storage pools later. With that mind mind here is my "easy" answer for 9.3 and 10.x. The installer "auto ZFS" has a 4k alignment option which I would assume works as advertised (having said that it would be simple to do a basic install and then examine that to confirm). For making subsequent pools, I simply set vfs.zfs.min_auto_ashift=12 is /etc/sysctl.conf, after which you will get 4k block alignment without messing with gnop. On 9.1 you had to do the gnop tricks but 9.3 supports the auto_ashift sysctl. On 9.3+, "zpool status" also *tells you* if you got the block alignment wrong, which is a big help over 9.1 where it could lurk undetected! G. --
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?55F2F2CF.3080004>