Date: Tue, 22 Dec 2009 13:22:21 +0100 From: Thomas Backman <serenity@exscape.org> To: =?iso-8859-1?Q?Dag-Erling_Sm=F8rgrav?= <des@des.no> Cc: Ollivier Robert <roberto@keltia.freenix.fr>, freebsd-current@freebsd.org, "James R. Van Artsdalen" <james-freebsd-current@jrv.org> Subject: Re: Some notes on RootOnZFS article in wiki Message-ID: <45929E18-EA48-4340-9954-683FF06B180B@exscape.org> In-Reply-To: <867hsf6xhh.fsf@ds4.des.no> References: <200912210600.46044.mel.flynn%2Bfbsd.current@mailing.thruhere.net> <20091221150514.GB75616@roberto-al.eurocontrol.fr> <4B2F9877.70201@jrv.org> <867hsf6xhh.fsf@ds4.des.no>
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On Dec 22, 2009, at 12:48 PM, Dag-Erling Sm=F8rgrav wrote: > "James R. Van Artsdalen" <james-freebsd-current@jrv.org> writes: >> Ollivier Robert <roberto@keltia.freenix.fr> writes: >>> On modern machines, system will boot from the GPT "freebsd-boot" >>> partition w/o having it active >> A correctly-written PC BIOS does not even look at (or for) a = partition >> table of any sort when booting. That's been the case for a >> quarter-century. A system that does not boot without the active bit >> set is buggy, not new vs. old. >=20 > Wrong, wrong, wrong. >=20 > Some MBRs look for the active bit, some don't. It doesn't mean = they're > buggy; it's a design decision. FWIW, ours does. >=20 > Some BIOSes *do* read the partition table; there was an issue some = years > ago with ThinkPads that froze at boot if you installed FreeBSD on them > because they misidentified the FreeBSD partition as a suspend-to-disk > partition. >=20 > DES Surely this doesn't contradict his statements in any way? He said that a correctly written *BIOS* doesn't look for at a partition = table; the fact that the FreeBSD MBR does is clearly irrelevant. I took = "system" to mean hardware/BIOS, by the way. The fact that some BIOSes do read it and freeze is obviously a bug, = further strengthening his argument that the BIOS shouldn't care about = the partition table. (I have this problem myself; I have two computers with nForce4 chipsets, = which cannot boot from GPT; if the disk channels aren't set to = "disabled" in the BIOS, it freezes on POST. You can have GPT storage = disks, if you disable the channels before plugging the disks in, but it = won't boot from a disk it doesn't find.) Regards, Thomas
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