HP Application Recovery Manager software A.06.10 Concepts guide (March 2008)

Figure 3 Disk virtualization with RAID
Various RAID levels are available, providing different levels of data redundancy,
speed, and access time. In some cases, it is possible to adjust the balance between
these attributes according to the amount of free storage available.
RAID systems operate by distributing data across the physical disks and presenting
them to the host as logical units, which, in turn, can be regarded as the physical
disks considered in the previous disk virtualization illustration. What are finally
presented to the host operating system after virtualization are again virtual disks, or
storage volumes.
Replication techniques
Basic replication can be performed in three contexts: local, remote, and remote plus
local.
Using Application Recovery Manager, only local replication is supported. An
additional enhancement of local replication is integration with HP–UX LVM mirroring.
From the operating system point of view, the contents of a replica of a particular
source volume are the same, whatever local replication (basic or using LVM mirroring)
is used to produce the replica. However, the method used can affect such things as:
• the speed of replication
• the amount of storage space used
• the impact on the application involved
Replication techniques22