242Creating volumes

Discovering the maximum size of a volume

max_nstripe=8 min_nstripe=2

#for RAID-5, by default create between 3 and 8 stripe columns max_nraid5stripe=8

min_nraid5stripe=3

#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 244 for more information.

Note: The maximum size of a VxVM volume that you can create is 256TB.

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).