Date: Thu, 28 Jan 2010 11:23:33 -0500 From: John Baldwin <jhb@freebsd.org> To: Dimitry Andric <dimitry@andric.com> Cc: freebsd-stable@freebsd.org, Brooks Davis <brooks@freebsd.org>, Dan Naumov <dan.naumov@gmail.com>, freebsd-questions@freebsd.org, Robert Noland <rnoland@freebsd.org> Subject: Re: booting off GPT partitions Message-ID: <201001281123.33097.jhb@freebsd.org> In-Reply-To: <4B618270.3050309@andric.com> References: <cf9b1ee01001270845j772d5524tbc2cbd53e70890a7@mail.gmail.com> <1264680406.2869.72.camel@balrog.2hip.net> <4B618270.3050309@andric.com>
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On Thursday 28 January 2010 7:26:24 am Dimitry Andric wrote: > On 2010-01-28 13:06, Robert Noland wrote: > > John or Marcel can correct me, but I don't think that this is an issue. > > The bootstrap is located in the pmbr in sector 0 and the GPT headers and > > tables are in sectors 1 - 34. The bootstrap code knows how to read the > > GPT tables and can deal with> 2 tb lba's. > > Ah yes, I see it now. It uses EDD packets with the BIOS int 13 > interface, which apparently have a 64-bit LBA. This should support up > to 8 ZiB with 512-byte sectors... > > OTOH, I have no idea how well most BIOSes actually implement this. > Since many OSes simply don't support anything over 2^32 sectors, I would > not be amazed to find much BIOSes out there that behave the same. Or am > I too paranoid now? :) It should work fine. The GPT boot code was originally written specifically to supporting booting from RAID volumes > 2TB. I've tested it on mfi(4) volumes that large (though I didn't verify the individual LBAs of all the various bits read in by the bootstrap and loader were). I know that other folks ran into bugs until the ZFS GPT boot code was all made 64-bit clean and that they have since booted > 2TB ZFS volumes ok. -- John Baldwin
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