As I mentioned in my wrap-up of VMworld 2011, one of the shiny new VMware products to hit the shelves this year is the vSphere Storage Appliance, or VSA. The VSA delivers SAN-like features to small businesses that may not have the budget, staffing, or technical sophistication to purchase a real SAN.
But the initial release of the VSA is marred by a number of serious deployment and scalability limitations. The real story behind VMware's introduction of the VSA has less to do with the VSA itself and more with VMware's relationship with its partners and its parent company, EMC.
What is the VSA?
The vSphere Storage Appliance is a cluster of virtual machine appliances that offer local storage as a unified, highly redundant datastore. A VSA cluster can currently span either two or three vSphere hosts, and it uses network-based synchronous mirroring (RAID1) combined with local RAID10 on the hosts to ensure data availability and to deliver reasonable performance. The vSphere cluster hosts are then able to connect to the VSA cluster's datastores via NFS -- effectively allowing the hosts to see and share each other's storage in real time.
In a two-host deployment, the first appliance operates a datastore roughly half the size of its local storage while the other half is used to store a mirror image of the second host's datastore, thereby distributing the storage load across both hosts. When a third host is added to the picture, there are three total datastores with each host backing up one of the other two in a round-robin fashion.
At first glance, the VSA seems like a fairly logical step for VMware. Over the last few years VMware has migrated high-end features such as High Availability and vMotion (which both require shared storage) down to its entry-level vSphere Essentials Plus bundle. VMware allows its customer base to use those sought-after features without buying and deploying a SAN -- seems pretty cut and dried.
It's anything but simple. To begin with, HP, one of VMware's closest and most supportive partners, has been selling its own VSA (yes, even the same acronym) since it acquired LeftHand Networks back in 2008. HP's P4000 Virtual SAN Appliance is much more feature-rich than VMware's offering in a number of different ways. It doesn't have any of the scalability or deployment issues that the 1.0 release of VMware's VSA has. Plus, it's capable of array-based replication to other P4000 SANs and provides an easy VSA-to-physical P4000 migration path.
If there's already a good product that fits the niche and it's sold by a partner, why wouldn't VMware promote it rather than developing its own product?
For one thing, VMware is largely owned by EMC -- a direct and occasionally vicious competitor of HP's. I'd wager that hell would need to freeze over before an EMC property would promote a chunk of HP storage tech.