At a high level both of these products provide the same service(s) for the user. Certainly the two “leap-frog” each other in terms of features, but at this point in time, they are very close. Both of them are “Hyper-converged VMware appliances”, though Nutanix is able to support other hypervisors such as Hyper-V and KVM as well as VMware. Simplivity will allow large customers to utilize their own hardware, however, the customer must buy the Simplivity software as well as the OmniCube Accelerator Card for each server since the card is what does all of the writes in the Simplivity architecture.
From an architectural perspective both systems provide a “hyper-converged” solution made up of X86 servers with internal storage which are networked/clustered together. You grow the overall system by simply adding additional nodes to the cluster. As of this writing, Nutanix offers more different kinds of options for those nodes, giving the user more flexibility on how the clusters is gown. Both systems provide for multiple tiers of storage including SSD and HDDs and will automatically move hot data between tiers. It should be noted that Nutanix offers an interesting feature that Simplivity does not. Nutanix has the concept of “data locality”. With data locality, when you v-motion a VM to a different node in the cluster, Nutanix will move the datastore(s) for that VM to the same node (assuming there is space). This movement is done in the background, over time so as not to impact performance.
As of the latest version both systems provide deduplication of data natively built into the system. There is some discussion about which method of deduplication is “better”, however, in the end I believe that both will provide the user good deduplication results. Both systems also provide compression of data at the lower tiers.
Again, in regards to backups, replication, DR, etc. both system provide very similar features. Both systems allow for replication of deduplicated/compressed data thus providing “WAN optimization”, both systems provide for snapshots, and both systems replicate data within the cluster for data durability. Simpilivity is able to provide one feature that Nutanix is not currently able to support, and that is replication to the “cloud”. Specifically, Simplivity provides their software as a VM image running in AWS which can be federated to an Omnicube running in the users data center.
In regards to management. Both systems provide for a GUI management environment which allows the user to manage the entire footprint from a single pane of glass. Again, how this is implemented is somewhat different. Nutanix provides a somewhat traditional management GUI based on HTML 5 that can be used to manage the Nutanix system. Simplivity takes a different approach. Simplivity utilizes a Vcenter plug-in to manage the Simplivity Omicube. This ties Simplivity to VMware, and will make it more difficult to support other hypervisors.
In conclusion, I believe that the two products would provide effectively the same capabilities for most customers with the single exception of the AWS support that Simplivity provides. This support would provide the ability for customers to create a Hybrid cloud infrastructure that span the customers private cloud and the AWS public cloud.