HP Volume Shadowing for OpenVMS

Performance Information for Volume Shadowing

Performance During Steady State

Factors That Affect Performance of a Shadow Set 

• I/O access path (local versus remote)



• Size of I/O requests



• Data access patterns (random or sequential)



• Read-to-write ratio



• Shadow set configuration



• State of a shadow set (steady or transient)



• Whether or not you use the shadowing copy and merge performance assists (see Improving Performance for Merge and Copy Operations)



• Whether or not you use the minicopy operation (see Improving Performance for Merge and Copy Operations



• Other work load on the system utilizing common resources (CPUs, disks, controllers, interconnects)



• Striping (RAID) implementation

The following sections examine how the state of a shadow set and its configuration can affect resource utilization and performance. Some guidelines for controlling the use of system resources are also provided in Guidelines for Managing Shadow Set Performance. Because there is no significant difference in the performance of a nonshadowed disk and a one-member shadow set, all discussions that follow apply to multiple-member shadow sets.

Performance During Steady State