VERITAS Volume Manager 3.1 Administrator's Guide

Performance Monitoring
Performance Guidelines:
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Performance Guidelines:
This section contains information on Volume Manager features. Volume
Manager provides flexibility in configuring storage to improve system
performance. Two basic strategies are used to optimize performance
• assign data to physical drives to evenly balance the I/O load among
the available disk drives
• identify the most frequently accessed data and increase access
bandwidth to that data by using striping and mirroring
Volume Manager 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, a system administrator
typically attempts to balance I/O load among available disk drives. The
effectiveness of this approach can be limited by difficulty in anticipating
future usage patterns, as well as an inability to split file systems across
drives. For example, if a single file system receives most of the disk
accesses, placing that file system on another drive moves the bottleneck
to another drive.
Since Volume Manager can split volumes across multiple drives, a finer
level of granularity in data placement can be achieved. After measuring
actual access patterns, the system administrator can adjust file system
placement decisions. Volumes can be reconfigured online after
performance patterns have been established or have changed, without
adversely impacting volume availability.
Striping
Striping is a way of “slicing” data and storing it across multiple devices
in to improve access performance. Striping provides increased access
bandwidth for a plex. Striped plexes improveaccess performance for both
read and write operations.
If the most heavily-accessed volumes (containing file systems or
databases) can be identified, then performance benefits can be realized.