Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Volume Layouts in VxVM
18 VERITAS Volume Manager Administrator’s Guide
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.
The figure, “Example of Concatenation,” shows the concatenation of two subdisks from
the same VM disk. The blocks n, n+1, n+2 and n+3 (numbered relative to the start of the
plex) are contiguous on the plex, but actually come from two distinct subdisks on the
same physical disk.
The remaining free space in the subdisk, disk01-02, on VM disk, disk01, can be put to
other uses.