Date: Sun, 29 Jul 2018 14:02:12 -0700 (PDT) From: "Rodney W. Grimes" <freebsd-rwg@pdx.rh.CN85.dnsmgr.net> To: David Cross <dcrosstech@gmail.com> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Request for comments, new geom part type alias: freebsd-geom Message-ID: <201807292102.w6TL2Cq4062739@pdx.rh.CN85.dnsmgr.net> In-Reply-To: <CAM9edePaxdNazqBNC%2B=iKjApr1CrDr%2BZUn1OEj65vr6Z17btRg@mail.gmail.com>
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> I'd like to propose that we create a GPT partition for geom labeled > partitions (gmirror, gstripe, geli, etc.. anything that can be 'tasted' and > automatically determined.) called 'freebsd-geom'. > > There are numerous cases where you shouldn't have a raw geom on a disk (for > example, imagine a raid 10 of a filesystem with VMs on it..on a raw disk > its possible that the lead block happens to line up with a VM disk image or > anything else a BIOS may determine is bootable). > > So the question becomes which part id to use; IF its a mirror of a swap of > UFS it seems perfectly reasonable to use freebsd-swap or freebsd-ufs (if a > bit dangerous). If its a mirror or a geli then you can again be in the > situation where the boot blocks (or something else), in certain > circumstances mistakes these for raw filesystems with similarly calamitous > results. > > Given these, it seems a 'freebsd-geom' (or similar) seems entirely > appropriate; we can mark these for what they really are, and eliminate > these cases where the system misinterprets intentions based on ambiguous > data. Do you have more details on just how your going to implement a "GPT" partition for geom labeled partitions. Though I think I understand what it is you want to do, how you describe it leads to some confusion on just what you are desiring to do. I am aware of some major issues involving gmultipath (GEOM::MULTIPATH) and gpt partitioned disks (GEOM::GPT) that due to bad tasting priorities you get bogus GPT error messages during boot if you have labeled your gmultipath devices, and infact can damage a gpt disk if you apply a multipath label onto a valid gpt disk. Please describe the "ambiguous data" as well, as I am not aware of what that would be. Thanks, -- Rod Grimes rgrimes@freebsd.org
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