This letter indicates which device the partition is on. For example, `/dev/sda` for the first hard disk, `/dev/sdb` for the second, and so on.
The final number denotes the partition. The first four (primary or extended) partitions are numbered `1` through `4`. Logical partitions start at `5`. So, for example, `/dev/sda3` is the third primary or extended partition on the first hard disk, and `/dev/sdb6` is the second logical partition on the second hard disk.
Even if your system can identify and refer to all types of disk partitions, it might not be able to *read* the file system and therefore access stored data on every partition type. However, in many cases, it is possible to successfully access data on a partition dedicated to another operating system.
Disk Partitions and Mount Points
Each partition is used to form part of the storage necessary to support a single set of files and directories. This is done by associating a partition with a directory through a process known as _mounting_. Mounting a partition makes its storage available starting at the specified directory (known as a _mount point_).
For example, if partition `/dev/sda5` is mounted on `/usr/`, that would mean that all files and directories under `/usr/` physically reside on `/dev/sda5`. So the file `/usr/share/doc/FAQ/txt/Linux-FAQ` would be stored on `/dev/sda5`, while the file `/etc/gdm/custom.conf` would not.
Continuing the example, it is also possible that one or more directories below `/usr/` would be mount points for other partitions. For instance, a partition (say, `/dev/sda7`) could be mounted on `/usr/local/`, meaning that `/usr/local/man/whatis` would then reside on `/dev/sda7` rather than `/dev/sda5`.
How Many Partitions?
At this point in the process of preparing to install {PRODUCT}, you should give some consideration to the number and size of the partitions to be used by your new operating system. However, there is no one right answer to this question. It depends on your needs and requirements.
Unless you have a reason for doing otherwise, you should *at least* create a `/boot` partition and a `/` (root) partition. Depending on your system's hardware specifications, additional partitions may be necessary, such as `/boot/efi` for 64-bit AMD and Intel systems with UEFI firmware, a `biosboot` partition for AMD and Intel systems with a GUID Partition Table (GPT) label on the system disk, or a `PReP Boot` partition on IBM Power Systems servers.
See xref:install/Installing_Using_Anaconda.adoc#sect-installation-gui-manual-partitioning-recommended[Recommended Partitioning Scheme] for more information about the recommended partitioning scheme.