VERITAS Volume Manager 4.1 Administrator's Guide

Understanding VERITAS Volume Manager
Volume Layouts in VxVM
Chapter 126
NOTE Although a volume can have a single plex, at least two plexes are
required to provide redundancy of data. Each of these plexes must
contain disk space from different disks to achieve redundancy.
When striping or spanning across a large number of disks, failure of any
one of those disks can make the entire plex unusable. Because the
likelihood of one out of several disks failing is reasonably high, you
should consider mirroring to improve the reliability (and availability) of
a striped or spanned volume.
See “Creating a Mirrored Volume” on page 242 for information on how to
create a mirrored volume.
Striping Plus Mirroring (Mirrored-Stripe or
RAID-0+1)
NOTE You may need an additional license to use this feature.
VxVM supports the combination of mirroring above striping. The
combined layout is called a mirrored-stripe layout. A mirrored-stripe
layout offers the dual benefits of striping to spread data across multiple
disks, while mirroring provides redundancy of data.
For mirroring above striping to be effective, the striped plex and its
mirrors must be allocated from separate disks.