Date: Sun, 29 Jul 2018 20:52:35 -0400 From: David Cross <dcrosstech@gmail.com> To: "Rodney W. Grimes" <freebsd-rwg@pdx.rh.CN85.dnsmgr.net> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Request for comments, new geom part type alias: freebsd-geom Message-ID: <144DA23D-26CF-4293-AE97-54CC8D6B52E3@gmail.com> In-Reply-To: <201807292102.w6TL2Cq4062739@pdx.rh.CN85.dnsmgr.net> References: <201807292102.w6TL2Cq4062739@pdx.rh.CN85.dnsmgr.net>
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Just a named GPT UUID type, like freebsd-swap, freebsd-ufs As for ambiguous data: consider you have a RAID 10 of a UFS filesystem. If you put that into freebsd-ufs freebsd-boot will see that and potentially attempt to boot it. If you have a raw raid gstripe, what shows up to the BIOS as to what this drives is depends entirely on the _contents_ of the drive at a specific position, information that could be controlled by a user. So to 'the bios' the meaning is what the OS put there, but the OS put user data there; how does the OS control the intent (as the BIOS sees it) of that data? On Jul 29, 2018, at 17:02, Rodney W. Grimes <freebsd-rwg@pdx.rh.CN85.dnsmgr.net> wrote: >> 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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