Veritas Storage Foundation Cross-Platform Data Sharing 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008

10 Overview of CDS
General concepts
Shared data across platforms
While volumes can be exported across platforms, the data on the volumes can be
shared only if data sharing is supported at the application level. That is, to make
data sharing across platforms possible, it must be supported throughout the
entire software stack.
For example, if a VxFS file system on a VxVM volume contains files comprising a
database, then the following functionality applies:
■ Disks can be recognized (as cds disks) across platforms.
■ Disk groups can be imported across platforms.
■ The file system can be mounted on different platforms.
However, it is very likely that, because of the inherent characteristics of
databases, you may not be able to start up and use the database on a platform
different from the one on which it was created.
An example is where an executable file, compiled on one platform, can be
accessed across platforms (using CDS), but may not be executable on a different
platform.
Note: You do not need a file system in the stack if the operating system provides
access to raw disks and volumes, and the application can utilize them. Databases
and other applications can have their data components built on top of raw
volumes without having a file system to store their data files.
Disk drive sector size
Sector size is an attribute of a disk drive (or SCSI LUN for an array-type device),
which is set when the drive is formatted. Sectors are the smallest addressable
unit of storage on the drive, and are the units in which the device performs I/O.
The sector size is significant because it defines the atomic I/O size at the device
level. Any multi-sector writes which VxVM submits to the device driver are not
guaranteed to be atomic (by the SCSI subsystem) in the case of system failure.