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

Chapter 1, Understanding VERITAS Volume Manager

Volume Layouts in VxVM

below that, and so on for the length of the columns. Equal-sized stripe units are used for

each column. For RAID-5, the default stripe unit size is 16 kilobytes. See “Striping

(RAID-0)” on page 21 for further information about stripe units.

VERITAS Volume Manager RAID-5 Array

Note Mirroring of RAID-5 volumes is not supported.

See “Creating a RAID-5 Volume” on page 217 for information on how to create a RAID-5

volume.

Left-Symmetric Layout

There are several layouts for data and parity that can be used in the setup of a RAID-5

array. The implementation of RAID-5 in VxVM uses a left-symmetric layout. This

provides optimal performance for both random I/O operations and large sequential I/O

operations. However, the layout selection is not as critical for performance as are the

number of columns and the stripe unit size.

Left-symmetric layout stripes both data and parity across columns, placing the parity in a

different column for every stripe of data. The first parity stripe unit is located in the

rightmost column of the first stripe. Each successive parity stripe unit is located in the

Column 0 Column 1 Column 2 Column 3

SD SD

SD = Subdisk

Stripe 1

Stripe 2