IBM System Storage DS3500 Introduction And Implementation Manual page 99

Draft Document for Review March 28, 2011 12:24 pm
Figure 3-22 illustrates the layout of those components in the case of the AIX Logical Volume
Manager.
Figure 3-22 AIX Logical Volume Manager
Hierarchy of structures in disk storage
A hierarchy of structures is used to manage the actual disk storage, and there is a well
defined relationship among these structures.
In AIX, each individual disk drive is called a physical volume (PV) and has a name, usually
/dev/hdiskx (where x is a unique integer on the system). In the case of the DS3500 Storage
System, such physical volumes correspond to a LUN.
Every physical volume in use belongs to a volume group (VG) unless it is being used as a
raw storage device.
Each physical volume is divided into physical partitions (PPs) of a fixed size for that
physical volume.
Within each volume group, one or more logical volumes (LVs) are defined. Logical
volumes are groups of information located on physical volumes. Data on logical volumes
appear contiguous to the user, but can be spread (striped) on multiple physical volumes.
Each logical volume consists of one or more logical partitions (LPs). Each logical partition
corresponds to at least one physical partition (see Figure 3-23 on page 76). If mirroring is
specified for the logical volume, additional physical partitions are allocated to store the
additional copies of each logical partition.
Logical volumes can serve a number of system purposes (paging, for example), but each
logical volume that holds ordinary systems, user data, or programs, contains a single
journaled file system (JFS or JFS2). Each file system consists of a pool of page-size
blocks. In AIX Version 4.1 and later, a given file system can be defined as having a
fragment size of less than 4 KB (512 bytes, 1 KB, or 2 KB).
Chapter 3. IBM System Storage DS3500 Storage System planning tasks
7914DS3KPlanning_090710.fm
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