HP Veritas Volume Manager 5.0 -UX 11i v3 manual Striping, Mirroring

464Performance monitoring and tuning

Performance guidelines

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.

Figure 16-1shows 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.

Figure 16-1 Use of striping for optimal data access

HotVol

PL1 SD1

Cool volume

Another

volume

Disk 1

HotVol

PL1 SD2

Lightly used volume

Disk 2

HotVol

PL1 SD3

Home directory volume

Disk 3

HotVol

PL1 SD4

Less important volume

Disk 4

Mirroring

Note: You need a full 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.