Veritas Storage Foundation Portable Data Containers: Cross-Platform Data Sharing 5.0.1 Administrators Guide, HP-UX 11i v3, First Edition, November 2009

Alignment values

The disk group block alignment has two values: 1 block or 8k (8 kilobytes).

All CDS disk groups must have an alignment value of 8k.

All disk group versions before version 110 have an alignment value of 1 block,

and they retain this value if they are upgraded to version 110 or later.

A disk group that is not a CDS disk group, and which has a version of 110 and

later, can have an alignment value of either 1 block or 8k.

The alignment for all newly initialized disk groups in VxVM 4.0 and later releases

is 8k. This value, which is used when creating the disk group, cannot be changed.

However, the disk group alignment can be subsequently changed.

See “Changing the alignment of a non-CDS disk group” on page 34.

Note: The default usage of vxassist is to set the layout=diskalign attribute on

all platforms. The layout attribute is ignored on 8K-aligned disk groups, which

means that scripts relying on the default may fail.

Dirty region log alignment

The location and size of each map within a dirty region log (DRL) must not violate

the disk group alignment for the disk group (containing the volume to which the

DRL is associated). This means that the region size and alignment of each DRL

map must be a multiple of the disk group alignment, which for CDS disk groups

is 8K. (Features utilizing the region size can impose additional minimums and

size increments over and above this restriction, but cannot violate it.)

In a version 110 disk group, a traditional DRL volume has the following region

requirements:

■ Minimum region size of 512K

■ Incremental region size of 64K

In a version 110 disk group, a version 20 DCO volume has the following region

requirements:

■ Minimum region size of 16K

■ Incremental region size of 8K

Overview of CDS

Disk group alignment