Measures when Volume I/O Performance has not Reached Target
When the volume that is set with the Automated QoS Priority or a target response time does not reach the I/O performance target, lowering the Automated QoS Priority or making the target response time later is necessary.
If the performance target is not attained though the priority of contending volumes is lowered or the target response time is delayed, modifying the volume configuration may achieve the performance target. The following are the examples:
If multiple volumes with high priority are sharing one and the same resource, the resource gets highly loaded and a bandwidth per volume is reduced. In this case, allocating those respective volumes to multiple resources may improve I/O performance.
If the CM of RAID groups making up a Tier pool is different from the CM configuring host affinities, a communication between those CMs is required, so that appropriate I/O performance could not be achieved (cross access). In this case, matching the CM of RAID groups making up a Tier pool to the CM configuring host affinities may improve I/O performance.
I/O performance may increase by changing the RAID configuration within the Tier pool, such as increasing the number of disks that are configured with striping.
When linking with Automated Storage Tiering is disabled, I/O performance may be increased by enabling it. However, an increase in I/O performance can be expected by enabling this only if all of the following conditions are satisfied.
If the Execution Mode for Automated Storage Tiering is "Auto", and Automated Storage Tiering is enabled
If the Automated QoS Priority is not set to "Unlimited" or "No Set", or the target response time is not set to "0".
Even if the target response time is set, in addition, when I/O characteristics (read, write, random access, sequential access) are significantly biased, the target value may not be achieved. For this reason, it is necessary to set a target value based on the hardware performance information in accordance with the I/O characteristics. For this reason, based on the performance information of the ETERNUS Disk storage system, set the target value according to the I/O characteristics.
Measures when I/O Performance for Business Applications has not Reached Target
When the performance target of the business application is not achieved even if you achieve the performance target of the volume, change the Automated QoS Priority or the target response time of the volume that the business application uses. If the QoS achievement rate does not reach 100% after the change, review the hardware configuration for the following items.
When utilizing the Web Console:
Refer to "Change Configuration of Automated QoS Function" in the ETERNUS SF Web Console Guide.
When utilizing the Command Line Interface:
Execute the esfadm volume qosset command.
After changing the Automated QoS Priority or the target response time, confirm the performance information with the performance graph. Refer to "7.1.3 Confirmation and Measures for Achievement for Performance Objectives for Application" for the confirmation methods.
Considerations Regarding Performance Limitations of Storage Device
The Automated QoS function effectively uses the I/O performance of the ETERNUS Disk storage system in order to adjust the I/O load between businesses.
Since the limit point for a performance adjustment is the maximum I/O performance value for the ETERNUS Disk storage system, even if a performance target that exceeds the capability of the ETERNUS Disk storage system is set, this target is not reached.
Considerations when Using Advanced Copy Function
When using the Advanced Copy function of the ETERNUS Disk storage system, the I/O response from the server is greater than usual while/when copying, the bandwidth of the target volume is increased more than required, and adjustments take place by narrowing the bandwidth of other affected volumes more than necessary. Since there are possibilities that the I/O performance of the business applications that are using the affected volumes may be reduced more than necessary, stopping the Automated QoS functions, such as QuickOPC or REC, during the initial copying is recommended.
