Veritas Storage Foundation™ for Oracle 5.0.1 Administrator's Guide

# /opt/VRTS/bin/vxdg -g PRODdg adddisk PRODdg02=c4t0d0
# /opt/VRTS/bin/vxdg -g PRODdg adddisk PRODdg03=c4t0d1
# /opt/VRTS/bin/vxdg -g PRODdg adddisk PRODdg04=c4t0d2
About selecting a volume layout
Veritas Volume Manager offers a variety of layouts that allow you to configure
your database to meet performance and availability requirements. The proper
selection of volume layouts provides optimal performance for the database
workload.
An important factor in database performance is the tablespace placement on the
disks.
Disk I/O is one of the most important determining factors of your database's
performance. Having a balanced I/O load usually means optimal performance.
Designing a disk layout for the database objects to achieve balanced I/O is a crucial
step in configuring a database.
When deciding where to place tablespaces, it is often difficult to anticipate future
usage patterns. VxVM provides flexibility in configuring storage for the initial
database set up and for continual database performance improvement as needs
change. VxVM can split volumes across multiple drives to provide a finer level of
granularity in data placement. By using striped volumes, I/O can be balanced
across multiple disk drives. For most databases, ensuring that different containers
or tablespaces, depending on which database you are using, are distributed across
the available disks may be sufficient.
Striping also helps sequential table scan performance. When a table is striped
across multiple devices, a high transfer bandwidth can be achieved by setting the
Oracle parameter DB_FILE_MULTIBLOCK_READ_COUNT to a multiple of full stripe
size divided by DB_BLOCK_SIZE.
See “About tuning VxVM ” on page 299.
How to choose appropriate stripe unit sizes
When creating a striped volume, you need to decide the number of columns to
form a striped volume and the stripe unit size. You also need to decide how to
stripe the volume. You may stripe a volume across multiple disk drives on the
same controller or across multiple disks on multiple controllers. By striping across
multiple controllers, disk I/O can be balanced across multiple I/O channels. The
decision is based on the disk and controller bandwidth and the database workload.
51Setting up databases
About selecting a volume layout