I've read many times that it's important to partition disks into smaller partitions, and that this is especially true for root or OS disks, but I've never been able to find a good reason for it. A commonly given excuse is that it improves data security: if your disk is divided into OS/data partitions (eg /, /usr, /usr/local, /home, etc, or on Windows C: (OS), D: (data)) and one fails, only that information is lost, and you can reinstall the OS or restore the data from backup without damaging the other information. Most of us (well, a lot of us) (well, some of us) use SSDs for the OS and a HDD for our data, and we all (probably) only partition each into a single partition anyway, so that argument seems specious, or at best primitive. Even if we don't use SSDs, HDDs are so cheap that using two separate drives is quite reasonable, so for the most part our disks only have a single partition on them anyway.Which brings me to the point of the post: why partition disks at all, even into a single disk-spanning partition? I've done some experiments lately and find that, while Windows can't do anything with an unpartitioned disk, Linux and some other Unices (OpenBSD not included) have no problem with it at all:# mkfs.ext4 /dev/sdbmke2fs 1.42.5 (29-Jul-2012)/dev/sdb is entire device, not just one partition!Proceed anyway? (y,n) yFilesystem label=OS type: LinuxBlock size=4096 (log=2)Fragment size=4096 (log=2)Stride=0 blocks, Stripe width=0 blocks262144 inodes, 1048576 blocks52428 blocks (5.00%) reserved for the super userFirst data block=0Maximum filesystem blocks=107374182432 block groups32768 blocks per group, 32768 fragments per group8192 inodes per groupSuperblock backups stored on blocks:        32768, 98304, 163840, 229376, 294912, 819200, 884736Allocating group tables: doneWriting inode tables: doneCreating journal (32768 blocks): doneWriting superblocks and filesystem accounting information: done# mount /dev/sdb /mnt# ls -l /mntdrwx------  2 root root 16384 Dec 10 06:30 lost+found/# mkdir /mnt/test# ls -l /mntdrwx------  2 root root 16384 Dec 10 16:30 lost+founddrwx------  2 root root  4096 Dec 10 16:31 test# umount /mntSo why bother?
Why partition disks?
partition