VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

Volume Layouts in VxVM
14 VERITAS Volume Manager Administrator’s Guide
Implementation of Layered Volumes
A layered volume is constructed by mapping its subdisks to underlying volumes. The
subdisks in the underlying volumes must map to VM disks, and hence to attached
physical storage.
Layered volumes allow for more combinations of logical compositions, some of which
may be desirable for configuring a virtual device. Because permitting free use of layered
volumesthroughoutthe command levelwouldhave resulted in unwieldyadministration,
some ready-made layered volume configurations are designed into VxVM. See “Layered
Volumes” on page 30 for more information.
These ready-made configurations operate with built-in rules to automatically match
desired levels of service within specified constraints. The automatic configuration is done
on a “best-effort” basis for the current command invocation working against the current
configuration.
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.