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

Performance Guidelines
282 VERITAS Volume Manager Administrator’s Guide
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 canincreaseaccess bandwidth to this data by striping it acrossportions of
multiple disks.
The figure “Use of Striping for Optimal Data Access” shows an example of a single
volume (HotVol) that has been identified as a data-access bottleneck. This volume is
striped across four disks, leaving the remaining space on these disks free for use by
less-heavily used volumes.
Use of Striping for Optimal Data Access
Mirroring
Note You may need an additional license to use this feature.
Mirroring stores multiple copies of data on a system. When properly applied, mirroring
provides continuous availability of data and protection against data loss due to physical
media failure. Mirroring improves the chance of data recovery in the event of a system
crash or the failure of a disk or other hardware.
In some cases, you can also use mirroring to improve I/O performance. Unlike striping,
the performance gain depends on the ratio of reads to writes in the disk accesses. If the
system workload is primarily write-intensive (for example, greater than 30 percent
writes), mirroring can result in reduced performance.
HotVol HotVol
PL1 SD3
Another
Disk 1 Disk 2 Disk 3 Disk 4
HotVol
PL1 SD4
Less
Important
Volume
HotVol
PL1 SD2
Lightly
Used
Volume
Home
Directory
Volume
Cool Volume
PL1 SD1
Volume