18.1 About Disk Partitions

Partitioning a disk drive divides it into one or more reserved areas (partitions) and stores information about these partitions in the partition table on the disk The operating system treats each partition as a separate disk that can contain a file system.

Oracle Linux requires one partition for the root file system. It is usual to use two other partitions for swap space and the boot file system. On x86 and x86_64 systems, the system BIOS can usually access only the first 1024 cylinders of the disk at boot time. Configuring a separate boot partition in this region on the disk allows the GRUB bootloader to access the kernel image and other files that are required to boot the system.

You can create additional partitions to simplify backups, to enhance system security, and to meet other needs, such as setting up development sandboxes and test areas. Data that frequently changes, such as user home directories, databases, and log file directories, is typically assigned to separate partitions to facilitate backups.

The partitioning scheme for hard disks with a master boot record (MBR) allows you to create up to four primary partitions. If you need more than four partitions, you can divide one of the primary partitions into up to 11 logical partitions. The primary partition that contains the logical partitions is known as an extended partition. The MBR scheme supports disks up to 2 TB in size.

On hard disks with a GUID Partition Table (GPT), you can configure up to 128 partitions and there is no concept of extended or logical partitions. You should configure a GPT if the disk is larger than 2 TB.

You can create and manage MBRs by using the fdisk command. If you want to create a GPT, use parted instead.


When partitioning a block storage device, align primary and logical partitions on one-megabyte (1048576 bytes) boundaries. If partitions, file system blocks, or RAID stripes are incorrectly aligned and overlap the boundaries of the underlying storage's sectors or pages, the device controller has to modify twice as many sectors or pages than if correct alignment is used. This recommendation applies to most block storage devices, including hard disk drives (spinning rust), solid state drives (SSDs), LUNs on storage arrays, and host RAID adapters.