Applies to: QSM 4 and XEVO 3 #

Why does QSM 4 show around 40% CPU usage when idle? #

QSM 4 may report CPU usage of around 40% even when no host I/O is taking place. This can be expected behavior due to the software design, which keeps the system ready to process incoming I/O and helps reduce initial response latency.

How to troubleshoot a drop in storage performance? #

If storage performance is lower than expected, follow these steps to help identify the cause:

1. Where supported, test with a direct connection between the host and storage system to help isolate potential switch-related issues. Schedule a maintenance window if connection changes may interrupt storage access.
2. Review the host’s firewall and antivirus settings for rules or scanning activity that may affect storage traffic or I/O performance.
3. Run Iometer cache-hit performance tests to help assess performance under controlled conditions. These results may differ from application performance.
4. Review the applicable recommendations in the QSAN Storage Performance Tuning Guide, then repeat the test using the same workload and settings to compare results.

Applies to: QSM 4 #

Why is file system performance lower than expected on XN5? #

File system performance may be lower than expected if the QFS file system is mounted on a different controller from the one handling the cluster IP, even when the pool owner and cluster IP are on the same controller.

To check the configuration:

1. Connect to Controller 1 via SSH and run the following command: qfs_mgr list
2. Check the mount status of the affected QFS file system. A status of YES indicates that it is mounted on Controller 1.
3. Verify that the cluster IP uses the optimized path through the controller where the QFS file system is mounted.