Veritas Storage Foundation™ for Oracle 5.0.1 Graphical User Interface Guide

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 “Tuning for Performance” in the Veritas Storage Foundation for Oracle
Administrator's Guide.
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.
In general, for most OLTP databases, use the default stripe unit size of 64 K or
smaller for striped volumes and 16 K for RAID-5 volumes.
How to choose between mirroring and RAID-5
VxVM provides two volume configuration strategies for data redundancy:
mirroring and RAID-5. Both strategies allow continuous access to data in the event
of disk failure. For most database configurations, we recommend using mirrored,
striped volumes. If hardware cost is a significant concern, but having higher data
availability is still important, use RAID-5 volumes.
RAID-5 configurations have certain performance implications you must consider.
Writes to RAID-5 volumes require parity-bit recalculation, which adds significant
Managing your database
About selecting a volume layout
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