Roderick said on Fri, 19 Sep 2025 16:12:34 +0000 >Are there (dis)advantages of UEFI over BIOS on an installation? > >I need the computer only for desktop with OpenBSD, no 24h server. > >By the way, are there restriction on the size of root / its position >in the HDD? > >Are there recommendations?
Short answer: When I have a choice, I prefer MBR over UEFI. Longer answer: My understanding is that all computers have a BIOS. It's the long term memory, on the motherboard, that remembers things like DRAM timings, processor speed adjustments, etc. MBR is both a boot scheme and a partitioning scheme. As a partitioning scheme, it's limited to disks 2TB or smaller. If used on a bigger disk, only 2TB is available, which of course is a waste. MBR only supports 7 partitions, but as I'll explain later, that's not really a problem. MBR is contained on the first 512 bytes of the disk, so it's very easy to back up and restore using dd. GPT is a partitioning scheme which can handle a disk a billion TB, so it will be many years before we outgrow it. It's what you use on disks more than 2TB. It can also handle disks much smaller than 2TB. You cannot do MBR booting on a GPT partitioned disk. I like GPT a lot. UEFI is a booting scheme that goes along with GPT partitioned disks but can't be used with MBR partitioned disks. UEFI uses hardware on the motherboard, blended with files in /boot/efi and UEFI settings available via the bios. UEFI is a very complicated specification, so many motherboard manufacturers get it wrong, to the extent that on some computers if you delete files from /boot/efi or delete /boot/efi itself, you can permanently brick the computer. I dislike UEFI. To get the best of both world, you can have a <2TB NVMe or SSD as the boot drive, and a big honking 20TB spinning rust drive for data, which you partition to have only one disklabel. The NVMe can be partitioned and booted MBR, while the 20TB can be partitioned GPT. Remember the 7 partition limit of MBR? No problem: If you need 40 "partitions" or disklabels or whatever, just make 40 localhost NFS mounts to various directories on the spinning rust, and you have "rubber partitions" that shrink and grow according to needs. So / is on the NVMe, as is /etc/ and /usr/ and /bin/ and /sbin/ and /libexec/ etc, while /home and other data is on these rubber directories. Of course, this setup pre-supposes that you have a desktop computer with enough space for a spinning rust drive. As others have said, some motherboards don't do MBR, ancient ones don't do NVME, and many have better or worse capabilities for both, so your mileage may vary. HTH, SteveT Steve Litt http://444domains.com
