Date: Fri, 27 Aug 2021 16:02:35 +0200 From: Javier <nixlist@outlook.es> To: freebsd-questions@freebsd.org Subject: Re: Paritioning scheme on MBR disk doubts Message-ID: <MW4PR01MB64019B5A0BF71C138BBD6554C4C89@MW4PR01MB6401.prod.exchangelabs.com> In-Reply-To: <20210827071306.34e90c17@archlinux> References: <MW4PR01MB640175FEDE09CAD451A9AA0BC4C79@MW4PR01MB6401.prod.exchangelabs.com> <20210826203921.0d3537684706867aef1e30f9@sohara.org> <20210827071306.34e90c17@archlinux>
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On Fri, 27 Aug 2021 07:13:06 +0200 Ralf Mardorf <ralf-mardorf@riseup.net> wrote: > On Thu, 26 Aug 2021 20:39:21 +0100, Steve O'Hara-Smith wrote: > >Unless MBR has changed since I last looked there could only be one > >extended partition(slice) and it had to be the fourth. Other than > >that this should work. > > Sometimes limits are not caused by the MBR. Some limits are probably > caused by partitioning tools, bootloaders, operating systems or are > just an issue of linguistic usage. TL;DR: Anyway, all this makes me ask now... does FreeBSD have any kind of limitation I could suffer in the way the MBR implementation is setup/programmed? Hi, and so might be. I've spent this night reading here and there to find out any documentation that really tells if that limitation is real or not and..., first, there isn't such; and second, I found that all depends on implementations by anyone. For example, here (Linux doc project) tell there is not limit on Extended location, but they tell the limit might be 15 logicals. https://tldp.org/LDP/sag/html/partitions.html (section 5.9.2 and figure 5-2) Fact, I tested on a virtual machine such limitations, and... 15 isn't the limit and even Windows 98 accepts over 20 logical partitions. I also took the oportunity to set the extended partition "anywhere" (actually 3rd) and no problem. Also I used the FreeBSD boot-only, and the partition tool didn't have any problem with such strange disk organization and re-organizations with it. Would be problems inside FreeBSD? Might be good to know. Then I found a page and... god, I didn't save to bookmarks!!!, where it told the limit is 20, but I set 21 logical partitions and I hadn't any problem either. I thought it was the following page, but, anyway, is helpful. It tells, too, that extended can be anywhere (second page): https://thestarman.pcministry.com/asm/mbr/PartTables.htm After all, an extended primay partition is set to a fixed size, so, it is only constrained by that size, and it doesn't matter the location, except other limits like booting some OSs that require the first to be primary and active (that isn't standard either, by what I read). Another reading about it: https://www.win.tue.nl/~aeb/partitions/partition_types-2.html But, in the end, all these pages seems to tell that, as there wasn't an starndard per-se, all depends on implementations. Good or bad. Anyway, all this makes me ask now... does FreeBSD have any kind of limitation I could suffer in the way the MBR implementation is setup/programmed? Regards. P.S.1: sorry these long posts, I think they worth, at least for the time I spent finding out the info :D P.S.2: BIOS Boot Specification, if anyone wants a read :D http://www.reenigne.org/crtc/PC-XT.pdf
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