From owner-freebsd-arch@FreeBSD.ORG Sat Dec 6 23:31:50 2008 Return-Path: Delivered-To: arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 29BC5106564A for ; Sat, 6 Dec 2008 23:31:50 +0000 (UTC) (envelope-from peter@wemm.org) Received: from wf-out-1314.google.com (wf-out-1314.google.com [209.85.200.172]) by mx1.freebsd.org (Postfix) with ESMTP id 067BF8FC13 for ; Sat, 6 Dec 2008 23:31:49 +0000 (UTC) (envelope-from peter@wemm.org) Received: by wf-out-1314.google.com with SMTP id 24so622168wfg.7 for ; Sat, 06 Dec 2008 15:31:49 -0800 (PST) Received: by 10.142.246.19 with SMTP id t19mr708601wfh.332.1228606309515; Sat, 06 Dec 2008 15:31:49 -0800 (PST) Received: by 10.142.255.21 with HTTP; Sat, 6 Dec 2008 15:31:49 -0800 (PST) Message-ID: Date: Sat, 6 Dec 2008 15:31:49 -0800 From: "Peter Wemm" To: "Marcel Moolenaar" In-Reply-To: <5783CEB0-6163-429E-8B28-2F9D6FBCF4A8@mac.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20081203.193714.693830802.imp@bsdimp.com> <200812041313.34565.jhb@freebsd.org> <5783CEB0-6163-429E-8B28-2F9D6FBCF4A8@mac.com> Cc: FreeBSD Arch Subject: Re: RFC: making gpart default X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 06 Dec 2008 23:31:50 -0000 On Thu, Dec 4, 2008 at 3:08 PM, Marcel Moolenaar wrote: > > On Dec 4, 2008, at 10:13 AM, John Baldwin wrote: > >> No, the way GPT works, you have a PMBR at sector 0, then immediately >> following >> that you have the Primary partition table in the next N sectors (the first >> sector in the table has a header that contains the size of the table). >> Then >> you have a backup Secondary partition table in the last N sectors of the >> disk >> as well. At least with the old gpt(8) tool you could actually tell it how >> big of a table to make when you created a GPT, and I imagine gpart >> probably >> can do the same. > > Yes. For schemes that support it, you can specify how many entries > to allocate. The 34 corresponds to 128 entries for GPT (4 entries > per sector)... Yes. 1 sector (pmbr) 1 sector (header) 32 sectors (128 partitions) = 34 sectors. Or we could have 1 sector (pmbr) 1 sector (header) 62 sectors (248 partitions) = 64 sectors. At least it is a power of two, even if only 32K. I'd love it if the man page told users to reserve another 32K for "boot code", so that the start address becomes sector 128, or 64K. This is a commonly used stripe size. -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV "All of this is for nothing if we don't go to the stars" - JMS/B5 "If Java had true garbage collection, most programs would delete themselves upon execution." -- Robert Sewell