Limitations of Volume Migration
You should keep in mind that Volume Migration operations can improve performance in one area while decreasing performance in another. Consider the following scenario:
- Parity Group A has an average usage value of 20%
- Parity Group B has an average usage value of 90%
Through Volume Migration, it is estimated that if one volume from Parity Group B is migrated to Parity Group A, the usage values of both parity groups become 55%. In this scenario, the I/O response time for Parity Group B will most likely decrease, while the I/O response time for Parity Group A will most likely increase. Overall, the throughput may increase or decrease.
Volume Migration must only be performed when you can expect a large improvement in storage system performance. Volume Migration operations may not provide significant improvement for cases in which parity group or volume usage varies only slightly, or for cases in which the overall MP usage is relatively high.
When an error condition exists in the VSP Gx00 models and VSP Fx00 models storage system, resource usage can increase or become unbalanced. Do not use data collected during an error condition as the basis for planning Volume Migration operations.