Date: Fri, 12 Aug 2016 23:58:12 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org>, freebsd-hackers@FreeBSD.org Subject: Re: on BIOS problems with disks larger than 2 TB Message-ID: <c69979b3-02ce-0d38-57b0-8996a658e366@FreeBSD.org> In-Reply-To: <490347865.SvN7iQoFWI@ralph.baldwin.cx> References: <6cec427b-4df1-50f0-3014-a96e5f8210f5@FreeBSD.org> <490347865.SvN7iQoFWI@ralph.baldwin.cx>
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On 12/08/2016 22:18, John Baldwin wrote: > Hmm, I'm not sure how easy it is to handle this case (i.e. how do you know > if an LBA beyond the size is really legit due to truncation vs coming from > corrupted metadata). Related is that tsoome's bcache stuff wants to know > where the end of the disk is (to avoid reading off the end), so just > ignoring the size is not easy. One idea that I have in mind but haven't really explored yet is for GPT formatted disks. Basically, if a GPT label hints that the disk size is larger than what BIOS reports, then we could try to read a backup label and if it matches what we expect, then we could adjust the size. Hmm, I think I recall that a long time ago some BIOSes used to do something similar with MBR :-) -- Andriy Gapon
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