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

Discovering the Maximum Size of a Volume
202 VERITAS Volume Manager Administrator’s Guide
# by default, create 1 log copy for both mirroring and RAID-5 volumes
nregionlog=1
nraid5log=1
# by default, limit mirroring log lengths to 32Kbytes
max_regionloglen=32k
# use 64K as the default stripe unit size for regular volumes
stripe_stwid=64k
# use 16K as the default stripe unit size for RAID-5 volumes
raid5_stwid=16k
Discovering the Maximum Size of a Volume
To find out how large a volume you can create within a disk group, use the following form
of the vxassist command:
# vxassist [-g diskgroup] maxsize layout=layout [attributes]
For example, to discover the maximum size RAID-5 volume with 5 columns and 2 logs
that you can create within the disk group, dgrp, enter the following command:
# vxassist -g dgrp maxsize layout=raid5 nlog=2
You can use storage attributes if you want to restrict the disks that vxassist uses when
creating volumes. See “Creating a Volume on Specific Disks” on page 203 for more
information.
Disk Group Alignment Constraints on Volumes
Certain constraints apply to the length of volumes and to the numeric values of size
attributes that apply to volumes. If a volume is created in a disk group that is compatible
with the Cross-platform Data Sharing (CDS) feature, the volume’s length and the values
of volume attributes that define the sizes of objects such as logs or stripe units, must be an
integer multiple of the alignment value of 8 blocks (8 kilobytes). If the disk group is not
compatible with the CDS feature, the volume’s length and attribute size values must be
multiples of 1 block (1kilobyte).
To discover the value in blocks of the alignment that is set on a disk group, use this
command:
# vxprint -g diskgroup -G -F %align
By default, vxassist automatically rounds up the volume size and attribute size values
to a multiple of the alignment value. (This is equivalent to specifying the attribute
dgalign_checking=round as an additional argument to the vxassist command.)