VERITAS Volume Manager 3.5 Administrator's Guide (September 2004)

Performance Monitoring and Tuning
Performance Guidelines
Chapter 12386
Performance Guidelines
VxVM allows you to optimize data storage performance using the
following two strategies:
• Balance the I/O load among the available disk drives.
• Use striping and mirroring to increase I/O bandwidth to the most
frequently accessed data.
VxVM also provides data redundancy (through mirroring and RAID-5)
that allows continuous access to data in the event of disk failure.
Data Assignment
When deciding where to locate file systems, you, as a system
administrator, typically attempt to balance I/O load among available disk
drives. The effectiveness of this approach is limited by the difficulty of
anticipating future usage patterns, as well as the inability to split file
systems across drives. For example, if a single file system receives most
disk accesses, moving the file system to another drive also moves the
bottleneck to that drive.
VxVM can split volumes across multiple drives. This permits you a finer
level of granularity when locating data. After measuring actual access
patterns, you can adjust your previous decisions on the placement of file
systems. You can reconfigure volumes online without adversely
impacting their availability.
Striping
Striping improves access performance by cutting data into slices and
storing it on multiple devices that can be accessed in parallel. Striped
plexes improve access performance for both read and write operations.
Having identified the most heavily accessed volumes (containing file
systems or databases), you can increase access bandwidth to this data by
striping it across portions of multiple disks.