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Old 28th June 2019
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jggimi jggimi is offline
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Join Date: May 2008
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Some general considerations. The MBR size limitation noted below is for for disks with 512-byte sectors.

MBR vs. GPT
  • MBR partition tables cannot address partitions above a 2TB limit. An OpenBSD MBR partition must exist entirely below the 2TB line. On larger drives, tt can only "extend" above the line by crafting the drive's disklabel(5) to exceed the MBR partition's boundaries. See the "b" option of the disklabel(8) editor.
  • Booting via MBR or GPT will be dependent upon the capabilities of the particular system's BIOS. Machines which pre-date EFI booting cannot boot via GPT at all, and there are newer systems which do not support "legacy" MBR booting.
  • From an OpenBSD installation administrative perspective, there's very little difference at installation time: merely select "g" to install a GPT when prompted to select MBR or GPT.
  • From an OpenBSD boot perspective, the console will use the EFI frame buffer driver, efifb(4). You'll still manage the console via the hardware-independent wscons(4) layer.
File systems
  • There are two "native" filesystems on OpenBSD: the Fast File System (FFS), and the Enhanced Fast File System (FFS2).
  • FFS2 is required for filesystems 2TB or larger.
  • FFS is required for the root filesystem.
  • The newfs(8) filesystem formatter will default to FFS for filesystems smaller than 1TB.
  • The newfs(8) filesystem formatter will default to FFS2 for filesystems 1TB or larger.
  • For clarity, when you run the installation script, it calls newfs(8) for you to format partitions.

Last edited by jggimi; 28th June 2019 at 11:52 PM. Reason: A little clarity. Note also that the FFS 2TB limit is with both 512 and 4096-byte sector sizes
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