Date: Sun, 30 Aug 2020 17:39:25 +0200 From: Polytropon <freebsd@edvax.de> To: "@lbutlr" <kremels@kreme.com> Cc: FreeBSD <freebsd-questions@freebsd.org> Subject: Re: (very OT) Ideal partition schemes (history of partitioning) Message-ID: <20200830173925.3d340cfb.freebsd@edvax.de> In-Reply-To: <AF89C1A4-FC9C-4065-B571-067BC2D0F69D@kreme.com> References: <CAGBxaXkf53K4EHtq9cDaRm3MOZZixyBq-aQfZ7upHo-wUwrmCg@mail.gmail.com> <AF89C1A4-FC9C-4065-B571-067BC2D0F69D@kreme.com>
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On Sun, 30 Aug 2020 04:18:48 -0600, @lbutlr wrote: > On 28 Aug 2020, at 21:08, Aryeh Friedman <aryeh.friedman@gmail.com> wrote: > > Also why are partitioned need at all? (both currently and historically) > > They are not needed now, and I don't think they provide any benefit, really. This is actually what "dedicated" means: no MBR, no GPT, just labels. And you are correct: Only _one_ label (i. e., one partition which is, in fact, no partition / slice) is required: the 'a' partition, defining it as a boot partition. For a single-OS install of FreeBSD this is possible. Now you might say: what about swap? No separate swap partition? You can use memory-backed or file-backed swap. Yes, all this has several restrictions and limitations, but from a purely technical point of view, it's absolutely possible. By the way, I do the same on "fill & stack" data disks: They only get one UFS filesystem directly to the device, no partitioning at all: "newfs <options> /dev/da0" - and it can be used. Sure, it does not boot, but data disks _don't_ boot. Can they be read in "Windows"? No, but FreeBSD data disks aren't read outside of FreeBSD. In this special case, only /dev/da0c (which equals /dev/da0) is created, and you can mount it as "mount -t ufs /dev/da0 /mnt". > Sure, you can do a multiple OS setup on a single drive with > partitions, but this is quite risky if Windows is involved which > is the main reason people want to do this. It's better to have > separated physical drives. That's often not as easy, especially when you use a laptop. But in such cases, it's sometimes more secure to use external USB (usually USB-C for better speed), to keep your regular workstation out of risk (at least try to). The problem with multiple systems on one disk is that they might not be able to boot from anything than a slice (a "DOS primary partition"), and there can only be up to 4 of them. Let's say you also need a boot manager - 1 slice gone, 3 remaining. One for FreeBSD, one for Linux, one for "Windows". If you need more, for example, if you want to have a dedicated data exchange partition or "shared /home", you will probably see "DOS extended partitions" and the "logical volumes" inside them as a possible solution. That might work for data, or subsequently mounted partitions (for example, if you have Linux and want to separate /usr, /var, /tmp, and such), but in most cases, those cannot hold a OS to _boot_ from, not because it wouldn't be possible to tell GRUB to load from that device (GRUB doesn't care, it just transfers control), but because the OS might expect to be run from a _primary_ partition and simply refuse to boot. Also note that in traditional DOS partitioning, only one of the 4 partitions can be marked "active", which indicates a bootable partition, and BIOS systems will tend to boot from the first one they find. Furthermore, this approach is quite static and does not easily allow to switch systems - that's where GRUB (or any other suitable boot manager for that matter) is the most useful part. > Historically they were quite important because partitions could > fail without the disk failing, and restoring a partition is > obviously much faster than restoring a whole drive. That is the reason why the programs dump and restore exist: They process data partition-wise (not at file level), so any VFS overhead can be avoided. Linear reads and writes are also an advantage if your backup media is sequencial access, such as tape. Backups were quite common, partially automated, scheduled, and required, so in case of severe drive problems, you loaded a new disk pack and restored from yesterday's tape backup. You are right - this is _not_ what people do today. :-) -- Polytropon Magdeburg, Germany Happy FreeBSD user since 4.0 Andra moi ennepe, Mousa, ...
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