Improving the performance of Dell Compellent SAN for VMware VMs
VirtuCache is software that improves the performance of Dell Compellent appliances without requiring you to upgrade the appliance or the SAN network. The performance improvement you will get from your Compellent appliance will rival an upgrade to an all-flash array.
Compellent appliances were the workhorses of the enterprise storage market a few years ago. They were cost effective at high capacities. The only drawback was that they are slower since they are primarily hard drive based, and when connected to VMware they exhibit all the ‘IO blender’ symptoms resulting in high VM level storage latencies.
VirtuCache is kernel mode driver software that will be installed in your VMware host that is connected to the Compellent appliance. You also need to install a SSD in the same VMware host. VirtuCache will then automatically cache frequently & recently used data – both reads and writes, from your Compellent appliance to this in-host SSD. Subsequently, we will automatically serve more and more storage requests from the in-host SSD, and by doing so we improve the performance of your Compellent appliance considerably.
With VirtuCache installed, if you experience under 10ms VM level latencies at all times regardless of how high or random the throughput, then VirtuCache is working as expected.
Sample Cost: Say you have a 100TB Compellent SAN shared by 10 ESXi hosts, then 2TB SSD per host as in-host cache should be sufficient. VirtuCache costs $3000/host for a perpetual license, add another $1000 for a 2TB enterprise grade SATA SSD (say Intel S4600). So for 10 hosts the total cost works out to $40000 for 20TB SSD cache capacity + VirtuCache. This is about a sixth of the cost of upgrading to a 100TB all-flash array. Also the SSD in our case will work better since it is closer to the CPU that consumes ‘hot’ data versus the SSD in the storage appliance, that is behind the network and the storage controller.