VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

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Performance Monitoring and Tuning
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Introduction
VERITAS Volume Manager (VxVM) can improve overall system performance by
optimizing the layout of data storage on the available hardware. This chapter contains
guidelines establishing performance priorities, for monitoring performance, and for
configuring your system appropriately.
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.
◆ Usestriping andmirroringtoincreaseI/O bandwidth tothemost frequentlyaccessed
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.