Over a year and a half ago I previewed VMware’s unreleased feature, Storage IO Control (SIOC). SIOC creates new intelligent latency metrics to evaluate the health of VMFS volumes. The same latency measurements are used in storage DRS, which VMware released in vSphere 5. While automated performance correction is great, vCenter should warn VMware admins when latency crosses defined thresholds. Custom vCenter alarms can do this.
With hardest work of making vSphere 5 generally available behind him, one of VMware’s engineers, Balaji Parimi, recently sent me scripts he wrote to create SIOC alarms. These alarms can be used to tell administrators that SIOC is throttling some virtual machines to save high priority applications from ailing datastores.
But in an effort to further obviate my own job, I will try and generalize the troubleshooting flow to add more clarity to the process.