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

Chapter 1, Understanding VERITAS Volume Manager

Volume Layouts in VxVM

VERITAS Volume ManagerRAID-5 Array

Note Mirroring of RAID-5 volumes is not currently supported.

See “Creating a RAID-5 Volume” on page 176 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

next stripe, shifted left one column from the previous parity stripe unit location. If there

are more stripes than columns, the parity stripe unit placement begins in the rightmost

column again.

Column 0 Column 1 Column 2 Column 3

SD SD

SD = Subdisk

Stripe 1

Stripe 2