VERITAS Volume Manager 4.1 Administrator's Guide

Understanding VERITAS Volume Manager
Volume Layouts in VxVM
Chapter 1 19
To achieve the desired storage service from a set of virtual devices, it
may be necessary to include an appropriate set of VM disks into a disk
group, and to execute multiple configuration commands.
To the extent that it can, VxVM handles initial configuration and on-line
re-configuration with its set of layouts and administration interface to
make this job easier and more deterministic.
Layout Methods
Data in virtual objects is organized to create volumes by using the
following layout methods:
• Concatenation and Spanning
• Striping (RAID-0)
• Mirroring (RAID-1)
• Striping Plus Mirroring (Mirrored-Stripe or RAID-0+1)
• Mirroring Plus Striping (Striped-Mirror, RAID-1+0 or RAID-10)
• RAID-5 (Striping with Parity)
The following sections describe each layout method.
Concatenation and Spanning
Concatenation maps data in a linear manner onto one or more subdisks
in a plex. To access all of the data in a concatenated plex sequentially,
data is first accessed in the first subdisk from beginning to end. Data is
then accessed in the remaining subdisks sequentially from beginning to
end, until the end of the last subdisk.
The subdisks in a concatenated plex do not have to be physically
contiguous and can belong to more than one VM disk. Concatenation
using subdisks that reside on more than one VM disk is called spanning.