From owner-freebsd-questions@FreeBSD.ORG Mon Dec 2 17:35:07 2013 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 490E22F2 for ; Mon, 2 Dec 2013 17:35:07 +0000 (UTC) Received: from oneyou.mcmli.com (oneyou.mcmli.com [IPv6:2001:470:1d:8da::100]) (using TLSv1 with cipher ADH-CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 0CCA3170F for ; Mon, 2 Dec 2013 17:35:07 +0000 (UTC) Received: from sentry.24cl.com (sentry.24cl.com [IPv6:2001:470:89e9:1:feed::1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "sentry.24cl.com", Issuer "Mike's Certificate Authority" (verified OK)) by oneyou.mcmli.com (Postfix) with ESMTPS id 3dYD3s5k9vz1DPw for ; Mon, 2 Dec 2013 12:35:05 -0500 (EST) Received: from BigBloat (bigbloat.24cl.home [10.20.1.4]) by sentry.24cl.com (Postfix) with ESMTP id 3dYD3r30GCz1Bjc for ; Mon, 2 Dec 2013 12:35:04 -0500 (EST) Message-ID: <201312021235030914.007AF1DF@smtp.24cl.home> In-Reply-To: <20131202182623.43331984.freebsd@edvax.de> References: <201311301303210813.05DE187E@smtp.24cl.home> <201312011121580096.005D00FB@smtp.24cl.home> <201312021213320528.00673D5F@smtp.24cl.home> <20131202182623.43331984.freebsd@edvax.de> X-Mailer: Courier 3.50.00.09.1098 (http://www.rosecitysoftware.com) (P) Date: Mon, 02 Dec 2013 12:35:03 -0500 From: "Mike." To: freebsd-questions@freebsd.org Subject: Re: gmirror, gpart and MBR vs GPT in the Handbook Content-Type: text/plain; charset="us-ascii" X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 02 Dec 2013 17:35:07 -0000 On 12/2/2013 at 6:26 PM Polytropon wrote: |On Mon, 02 Dec 2013 12:13:32 -0500, Mike. wrote: |> My understanding is that MBR can be used with drives only up to |> and including 2TB in size. So if I use MBR, the maximum drive |> size I could use would be 2TB. Is that correct? | |Don't confuse partitioning schemes and file systems. Both are |different things, happening on different "layers". To make it |simpler than it probably is: | |Partitioning = | a) MBR with classic tools (fdisk, bsdlabel) | b) MBR with modern tool (gpart) | c) GPT (gpart) | d) Dedicated (only the "bsdlabel part") | |RAID concepts = | a) mirror | b) stripe | c) combined and extended forms ... | |File system = | a) UFS | option +U: soft updates | option +J: journal | b) ZFS | |Of course ZFS can handle things like "RAID concepts" already |internally, whereas UFS would use gstripe and gmirror as |"little helpers" - it will run on top of them, i. e., you |initialize the device that represents the whole mirror |instead of individually dealing with the drives that the |mirror is constructed of. | |Regarding UFS's 2 TB limitation: | |http://www.freebsd.org/projects/bigdisk/ | |Additionally, MBR can be troublesome on bigger hard disks |or stripes. | |http://www.freebsd.org/doc/handbook/bsdinstall-partitioning.html | |Today's consensus seems to be: | |If you use ZFS, let ZFS deal with everything. | |If you use UFS, use gpart for preparation work. Use GPT when |possible, MBR only in exceptions, and dedicated if and only |if you really _really_ know what you're doing. :-) ============= Following the bsdinstall-partitioning link you cited, and then following a link on that page, I wind up here: http://en.wikipedia.org/wiki/Master_boot_record which states: "...The organization of the partition table in the MBR limits the maximum addressable storage space of a disk to 2 TB ...." That (and other places) is where I got the 2TB limit of MBR into my head. Am I misunderstanding that statement? Thanks.