Date: Sun, 13 Sep 2015 16:48:25 -0453.75 From: "William A. Mahaffey III" <wam@hiwaay.net> To: freebsd-questions@freebsd.org Subject: Re: followup storage question Message-ID: <55F5EDDF.8040108@hiwaay.net> In-Reply-To: <55F2F2CF.3080004@physics.umn.edu> References: <55F2D086.6060509@hiwaay.net> <55F2F2CF.3080004@physics.umn.edu>
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On 09/11/15 10:33, Graham Allan wrote: > 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. *Eeeeeeeeek* !!!!! [root@kabini1, /etc, 4:47:06pm] 332 % sysctl -A | grep ashift [root@kabini1, /etc, 4:47:10pm] 333 % uname -a FreeBSD kabini1.local 9.3-RELEASE-p24 FreeBSD 9.3-RELEASE-p24 #0: Sat Aug 22 01:54:44 UTC 2015 root@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64 [root@kabini1, /etc, 4:47:15pm] 334 % I don't see that sysctl setting, am I missing something (No ZFS installed on this box, BTW) ? Thanks & TIA & have a nice weekend. -- William A. Mahaffey III ---------------------------------------------------------------------- "The M1 Garand is without doubt the finest implement of war ever devised by man." -- Gen. George S. Patton Jr.
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