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Posts Tagged ‘managing UNIX hard drives’

The Logical Volume Manager With Unix Hard Drives

When I first started managing UNIX systems, I underestimated the amount of time I would spend managing disk space. Traditional UNIX operating systems let you divide disks into 8 or 16 partitions (also called slices). When a slice becomes full, you must either move data to another slice or repartition the disk to make that slice larger. Repartitioning is time-consuming because you must back up the disk, repartition it by modifying the disk label, and restore data as necessary.

A typical UNIX disk analyzer.

Logical-volume technology provides the ability to reserve disk space that can be added to slices as needed. You can increase the size of a slice on the fly without losing data or experiencing significant downtime.

Overview Of Logical Volumes

The examples shown are for an HP-UX 10.20 system. The concepts also apply to other systems, such as AIX, that support logical volumes.

A disk can be divided into logical volumes (analogous to physical partitions). However, a logical volume can span more than one physical disk. Logical volumes are grouped into logical volume groups. Logical volumes cannot span more than one logical volume group.

The first step to using logical volumes is to create a volume group. Next, disks are added to the logical volume group