HP-UX System Administrator's Guide: Overview HP-UX 11i v3 (B3921-90011, September 2010)

(Logical) Volumes
Once you have grouped physical disk drives into disk/volume groups, the collective space can
be divided into logical storage containers that can be smaller or larger than any individual drive
in the group. These logical storage containers are called:
• volumes, if you are using the VERITAS Volume Manager (VxVM)
or
• logical volumes, if you are using the Logical Volume Manager (LVM)
Once defined, individual volumes or logical volumes can be used for:
• booting (they can contain bootstrap loaders, offline diagnostics, and other software needed
for server administration purposes)
• file systems (traditional file storage)
• swap space (virtual memory / paging)
• dump space (memory dumps following a system panic)
• raw disk access (for use by database applications, and other applications that manage their
own disk space)
Logical volumes can be made larger or smaller as needed (if the data they contain support these
operations).
Figure 3-2 Logical Volumes can be Resized
¸
˚
file system
or
database
lvol2
lvol1
File Systems
If you are not using a volume (or physical disk) for swap space or raw disk access (for example
disk space managed by a database application), you are probably using it for file storage.
The directories, files, and file data are usually distributed throughout a volume or disk drive. In
the same way a card catalog allows you to locate a specific book in a large library, the primary
function of a file system is to maintain the pointers to the files stored in a volume or on a physical
disk so that those files can be later retrieved. These are not merely pointers indicating which file
is in which directory; these are the low level pointers and other vital information, for example:
• which disk blocks belong to which file
• which disk blocks are currently unused (so that specific disk blocks are not simultaneously
used for more than one purpose and order is maintained)
• linked lists of directory navigation information
File systems also have other important functions, for example maintaining ownership and access
privilege information so that HP-UX security functions can ensure that only those authorized to
access a file or directory can do so.
Storage on HP-UX 47