VERITAS Storage Foundation 4.1 Cross-Platform Data Sharing Administrator's Guide

Disk Group Alignment
8 VERITAS Storage Foundation CDS Administrator’s Guide
Alignment Values
The disk group block alignment has two values: 1 block or 8k (8 kilobytes).
Alignment Value 1
Note Disk groups with version numbers less than 110 are not supported for the Solaris OS on the
X86 platform.
All disk group versions before version 110 must have a alignment value of 1.
Disk groups have an alignment value of 1 after upgrading from pre-version 110 to version 110 or
later.
Encapsulated disks, which require disk cylinder alignment, have an alignment value of 1.
Non-CDS disk groups version 110 and later can have either a value of 1 block or 8k.
Alignment Value 8K
Non-CDS disk groups version 110 and later can have either a value of 1 block or 8k.
All CDS disk groups have an alignment value of 8k.
The alignment for all newly initialized disk groups in VxVM 4.0 or a later release is 8k. This value
(which is used when creating the disk group) cannot be changed. However, the disk group
alignment can be subsequently changed (refer to “Changing the Alignment of a Non-CDS Disk
Group” on page 25).
Note The default usage of vxassist is to set the layout=diskalign attribute on all
platforms. This is ignored on 8K-aligned disk groups, which means that scripts relying on
the default may fail.
Dirty Region Log (DRL) 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 must have:
◆ Minimum region size of 512K
◆ Incremental region size of 64K