Use case for many-to-many connections
The following figure shows an example of a network, called Network B, in which a production server and a development server are connected to the storage system in a many-to-many configuration. HBA wwn01 on the production server is connected to ports 1A, 2A, 1C, and 2C, and HBAs wwn02 and wwn03 on the development server are also connected to the same four ports. CHA is for , and CHB is for .
Before using Server Priority Manager, you must find the WWN (Worldwide Name) of each host bus adapter in host servers. WWNs are 16-digit hexadecimal numbers used to identify host bus adapters. For details on how to find WWNs, see the Provisioning Guide of your storage system.
When using Server Priority Manager, ensure that all host bus adapters connected to ports in the storage system are monitored. Use the WWN tab of the Server Priority Manager main window to monitor host bus adapters. Place host bus adapters connected to each port below the Monitor icons.
In Network B, each of the four ports in the storage system is connected to three host bus adapters (wwn01, wwn02, and wwn03). Place the host bus adapter icons of wwn01, wwn02, and wwn03 below the Monitor icons for all four port icons.
Server Priority Manager is not able to monitor and control the performance of hosts whose host bus adapters are placed below the Non-Monitor icon. Therefore, make sure to place host bus adapters below the Monitor icons.
The priority for the host bus adapters is set using the WWN tab of the Server Priority Manager main window. In Network B, the production server is high priority (Prio.), and the development server is low priority (Non-Prio.). To give priority to the three host bus adapters, take the following steps:
- On the WWN tab of the Server Priority Manager main window, select one of the four ports that the HBAs are connected to (that is, ports 1A, 1C, 2A, and 2C).
- Set Prio. to wwn01. Also, set Non-Prio. to wwn02 and wwn03.
The following figure shows the priority settings for host bus adapters. When you select port 1A and set the priority for host bus adapters, the same settings are automatically applied to the other ports (ports 1C, 2A, and 2C).
The term prioritized WWN to refers to a high-priority host bus adapter (for example, wwn01). The term non-prioritized port refers to a low-priority host bus adapter (for example, wwn02 and wwn03).
Monitor traffic between host bus adapter and ports. There are two types of traffic statistics: the I/O rate and the transfer rate. The I/O rate is the number of I/Os per second. The transfer rate is the size of data transferred between a host and the storage system per second. When you view traffic statistics in the window, you select either the I/O rate or the transfer rate. For Network B, you must do the following:
- Measure traffic between port 1A and the three host bus adapters (wwn01, wwn02, wwn03).
- Measure traffic between port 2A and the three host bus adapters (wwn01, wwn02, wwn03).
- Measure traffic between port 1C and the three host bus adapters (wwn01, wwn02, wwn03).
- Measure traffic between port 2C and the three host bus adapters (wwn01, wwn02, wwn03).
The following figure shows these settings on the WWN tab of the Server Priority Manager main window.
The I/O traffic between the ports and host bus adapters is now monitored. When the desired amount of data has been collected, the traffic statistics are reviewed on graphs using the Performance Monitor window. The following graph shows the measured I/O rate for the paths between each port and the host bus adapters. According to the data, the I/O rate for the path between port 1A and the prioritized WWN (wwn01) was approximately 400 IO/s at first, and the I/O rate for the path between port 1A and the non-prioritized WWNs (wwn02 and wwn03) was approximately 100 IO/s at first. However, as the I/O rate for the non-prioritized WWNs gradually increased from 100 IO/s to 200 IO/s, the I/O rate for the prioritized WWN decreased from 400 IO/s to 200 IO/s, which indicates a decrease in the performance of the prioritized WWN.
To maintain a higher I/O rate (400 IO/s) for the prioritized WWN, you can set upper limits on the I/O rate for the non-prioritized WWNs to minimize their effect on the performance of the high-priority production server. When an upper limit is set for the first time, it is recommended that the upper limit value be approximately 90 percent of the peak traffic level. In Network B, the peak I/O rate at the paths between each of the four ports and the non-prioritized WWNs (wwn02 and wwn03) is 200 IO/s, so the recommended upper limit for wwn02 and wwn03 is 720 IO/s (200 × 4 × 0.90). The following figure shows the result of setting the upper limit of 720 IO/s on the paths between port 1A and non-prioritized WWNs wwn02 and wwn03 on the WWN tab of the Server Priority Manager main window.
After upper limits have been applied, the traffic is measured again to check the result of the upper limits and see whether host performance has improved to a desirable level, in this case 400 IO/s for wwn01. If not, you can adjust the upper limit of non-prioritized WWNs to a smaller value until the I/O rate for wwn01 reaches the desirable level.
If you want to allow higher performance for non-prioritized WWNs when system activity is low, you can apply a threshold. For many-to-many connections you can specify one threshold for the entire storage system, regardless of the number of prioritized WWNs. For example, if there are three prioritized WWNs in the network and the threshold is 100 IO/s, the upper limit on the non-prioritized WWNs is disabled when the sum of the I/O rates for all three prioritized WWNs falls below 100 IO/s.
The following table shows the relationship between the thresholds of prioritized WWNs and the upper limits of non-prioritized WWNs.
|
Threshold settings |
Upper limit is set (non-zero) to the non-prioritized WWN |
Upper limit of the non-prioritized WWN = 0 |
|
Threshold is set to the prioritized WWN |
When thresholds are set to prioritized WWNs, depending on the I/O rate or the transfer rate, the following controls are executed.
|
The threshold control of the prioritized WWN is not executed. |
|
Threshold is not set to the prioritized WWN |
The specified upper limit is always in effect. |