A couple weeks ago Frank Denneman did a great post on why virtual appliances used for data path acceleration are not to be desired if you are trying to achieve low latency in your environment. Frank outlined why the use of a hypervisor kernel module provides a preferred way to accelerate I/O. I highly recommend you read his post before you go any further.
Even though virtual appliances are not the best at performance, there are still many reasons why you might want to deploy a VSA (Virtual Storage Appliance). For one reason it’s typically less cost and easier to manage. This is why you most likely see VSA’s in a smaller or test/dev environments. The ability to aggregate local storage into a shared pool is also a desired approach in using a VSA.
I recently did some testing with a well-known Virtual Storage Appliance along with PernixData’s Flash Virtualization Platform (FVP). I was amazed to find that this integration was truly a great way to implement storage capacity and performance. The VSA did what it does best; aggregate local storage into a capacity pool that can be easily managed, while FVP provided the performance required for the workloads.
Here is a simple diagram showing this use case…
This use case provides several options to accelerate I/O. As an example if you choose a “Write Through” policy then all writes from a given workload will be acknowledged from the VSA storage pool, while FVP accelerates the read I/O. However if you choose a “Write Back” policy then writes will be accelerated from the local flash devices in the cluster and then de-staged appropriately to the VSA storage pool. In addition the workload that you choose to accelerate could be VM’s located on the VSA or even the VSA itself! As what to choose for your environment, I will have a separate post outlining what types of scenarios work best given a FVP design choice.
This use case provides low latency and increased IOPs not typically seen with just a virtual appliance. So, depending on what your objective is and environment this could be the winning ticket for storage capacity and performance. Stay tuned for more ways to take advantage of FVP!!