A fear of cloud administrators is that some tenant or VM goes nuts and eats up a host’s bandwidth to the storage. System Center has the ability to deal with this. VMM Dynamic Optimization is like DRS in vSphere; it will load balance workloads at a triggered threshold. And Performance and Resource Optimization (PRO) allows OpsMgr to detect an immediate issue and instruct VMM to use Intelligent Placement to react to it.
But maybe we want to prevent the issue from happening at all. Maybe we want to cap storage bandwidth based on price bands – you pay more and you get faster storage. Maybe a VM has gone nuts and we want to limit the damage it does while we figure out what has gone wrong. Maybe we want alerts when certain VMs don’t have enough bandwidth; we could have an automated response in System Center to deal with that.
WS2012 R2 Hyper-V gives us Storage QoS. We can configure Storage QoS on a per-virtual hard disk basis using the IOPS measurement:
- Maximum: This is a hard cap on how many IOPS a virtual hard disk can perform
- Minimum alert: We will get an alert if a virtual hard disk cannot perform at this minimum level
The settings can be configured while a virtual machine is running. That allows a tenant to improve their plan and get more storage bandwidth.
Note: there are IOPS PerfMon counters to help you figure out what good and bad metrics actually are.