Data center initiatives, like server and desktop virtualization, as well as the introduction of flash enhanced storage, have motivated storage managers to upgrade their storage networks sooner than they might have planned. But those storage managers would be wise to consider more that just the link speed of the proposed network upgrade. As we discussed in a previous entry, “Maximum VM Density Requires Visibility“, end-to-end visibility is a key capability. In addition, the ability to control how bandwidth is allocated is also vitally important.
Controlling link speed is critical as the number of virtual machines (VM) per host increases, something we call VM density, and as an increasing variety of workloads (databases, VDI, server virtualization) all compete for the same shared storage resources. Controlling link speed, also known as Quality of Service (QoS), allows the storage manager to insure that mission critical applications get the performance they need. As a result, there is little argument that controlling link speed is vital, it is how to provide QoS that is in question.
Several storage system vendors have tried to provide QoS capabilities. While certainly better than no control, it is at the bottom of the storage hierarchy and there can certainly be contention further up the storage network stack that Storage System QoS might not be able to mitigate.
As we discussed in our recent webcast with Brocade entitled, “Storage Networking: Thinking Beyond Link Speed“, fiber channel storage networks can provide an excellent means to insure that mission critical VMs or even mission critical bare metal database servers can be guaranteed specific performance.
Fiber channel storage networks, via the use of buffer credits, can make sure that specific physical hosts and even VMs can be immune to a runaway VM that threatens to consume all of a storage infrastructures I/O resources. These capabilities can be used by themselves or in combination with the QoS capabilities of the hypervisor and the storage system, so that an end-to-end performance guarantee can be delivered.