Date: Mon, 17 Sep 2012 14:41:09 +0200 (CEST) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-hardware@FreeBSD.ORG, jhb@FreeBSD.ORG Subject: Re: Booting from 3TB drive (UFS, BIOS) Message-ID: <201209171241.q8HCf9Bm033095@lurza.secnetix.de> In-Reply-To: <201208151111.51123.jhb@freebsd.org>
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John Baldwin wrote: > On Tuesday, August 14, 2012 9:23:19 am Oliver Fromme wrote: > > I've got a small PC that currently has two disks: The > > first one is 1 TB with a standard MBR, used to boot FreeBSD, > > and the second one is 3 TB with GPT, used as data disk for > > FreeBSD (the BIOS doesn't have to care about this one at all > > because it's not used for booting). > > > > Now I would like to replace the first disk with a 3 TB one, > > too. However, will I be able to boot from it? The PC is > > not exactly a new one (ASRock A330GC with Atom 330 processor, > > a few years old) and has a standard BIOS (dated 07/16/2009). > > > > I understand that I will have to use GPT in order to be able > > to use the full capacity of 3 TB, and that I will have to > > install a pmbr to enable the BIOS to detect the disk as > > bootable. Is this correct? Will that work? (Assuming that > > the boot partition will have to be within the first 2 TB of > > the drive, of course.) > > A GPT boot should work, and the boot partition can even be > above 2 TB. (GPT booting only uses the EDD BIOS interface > which uses 64-bit LBAs, and the GPT boot code will use all > 64-bits of the LBAs stored in GPT, etc.) (I'm sorry for the late reply; I still haven't gotten around to upgrade the disks ...) Problem is, the machine doesn't have an EFI BIOS and does *not* support GPT. So it will use the compatibility MBR of the GPT, I assume. And MBR isn't able to represent addresses beyond 2 TB, so the slice containing the boot partition will have to be within the first 2 TB of the drive, right? I tried to research the issue, but Google mostly returns pages concerning Linux that advise to use disks > 2 TB as data disks only while using a separate disk <= 2 TB for booting, unless you have an EFI BIOS that supports GPT natively. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd "The most important decision in [programming] language design concerns what is to be left out." -- Niklaus Wirth
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