From owner-freebsd-stable@FreeBSD.ORG Thu Jul 22 04:20:08 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id EA069106566B for ; Thu, 22 Jul 2010 04:20:08 +0000 (UTC) (envelope-from spork@bway.net) Received: from xena.bway.net (xena.bway.net [216.220.96.26]) by mx1.freebsd.org (Postfix) with ESMTP id B53D88FC08 for ; Thu, 22 Jul 2010 04:20:08 +0000 (UTC) Received: (qmail 71694 invoked by uid 0); 22 Jul 2010 04:20:07 -0000 Received: from unknown (HELO ?10.3.2.41?) (spork@96.57.144.66) by smtp.bway.net with (DHE-RSA-AES256-SHA encrypted) SMTP; 22 Jul 2010 04:20:07 -0000 Date: Thu, 22 Jul 2010 00:20:07 -0400 (EDT) From: Charles Sprickman X-X-Sender: spork@hotlap.local To: Adam Vande More In-Reply-To: Message-ID: References: <4C47B57F.5020309@langille.org> User-Agent: Alpine 2.00 (OSX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-stable , Dan Langille Subject: Re: Using GTP and glabel for ZFS arrays X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 22 Jul 2010 04:20:09 -0000 On Wed, 21 Jul 2010, Adam Vande More wrote: > On Wed, Jul 21, 2010 at 10:05 PM, Dan Langille wrote: > >> Why '-b 34'? Randi pointed me to >> http://en.wikipedia.org/wiki/GUID_Partition_Table where it explains what >> the first 33 LBA are used for. It's not for us to use here. >> >> Where SOMEVALUE is the number of blocks to use. I plan not to use all the >> available blocks but leave a few hundred MB free at the end. That'll allow >> for the variance in HDD size. >> >> Any suggestions/comments? Is there any advantage to using the -l option on >> 'gpart add' instead of the glabel above? >> > > You'll want to make sure your partitions are aligned, discussion here(says > 4k drives, but info pertinent to all): > > http://lists.freebsd.org/pipermail/freebsd-hackers/2010-March/031154.html >From that thread: http://lists.freebsd.org/pipermail/freebsd-hackers/2010-March/031173.html (longer explanation) I'm not really understanding the alignment issue myself on a few levels: -Does it only affect the new drives with 4K blocks? -If it does not, is it generally good to start your first partition at 1MB in? How exactly does doing this "fix" the alignment issue? > My understanding is that you weren't booting from zfs, just using it as an > data file system. In that case, you'd want to use "gpart add -b 512 ..." > or some other multiple of 16. Even 1024 would be a good safe number. Also > GPT creates partitions not slices. Your resulting partitions with be > labeled something like ad0p1, ad0p2, etc. I assume the same can be applied if you do boot from zfs; you'd still create the "freebsd-boot" partition starting at 34, but your next partition (be it swap or zfs) would start either 512 or 1024 sectors in? Thanks, Charles > > > -- > Adam Vande More > _______________________________________________ > freebsd-stable@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org" >