Veritas Storage Foundation 5.1 SP1 Advanced Features Administrator"s Guide (5900-1503, April 2011)

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.
Block size issues
The block size is a platform-dependent value that is greater than or equal to the
sector size. Each platform accesses the disk on block boundaries and in quantities
that are multiples of the block size.
Data that is created on one platform, and then accessed by a platform of a different
block size, can suffer from the following problems:
■ The data may not have been created on a block boundary
compatible with that used by the accessing platform.
■ The accessing platform cannot address the start of the data.
Addressing issues
The size of the data written may not be an exact multiple of the block
size used by the accessing platform. Therefore the accessing platform
cannot constrain its I/O within the boundaries of the data on disk.
Bleed-over issues
Operating system data
Some operating systems (OS) require OS-specific data on disks in order to recognize
and control access to the disk.
CDS disk format and disk groups
This section provides additional information about CDS disk format and CDS disk
groups.
457Migrating data between platforms
CDS disk format and disk groups