Nice and slow!
And kids, this is why we don't buy traditional SANs anymore. They're slow!
VMware is claiming to be able to hit a peak of 7 million IOPs with their virtual SAN solution and with proper systems like Windows Storage Spaces or with OpenStack Swift, you can go way way past that.
The bottleneck in storage performance is centralized controllers like those found in SANs. They just aren't fast. Storage performance is bottlenecked by where dedpulication hashes are calculated. A SAN always does it at the storage controllers. VMware virtual SAN is just a distributed block based dedup file system. It's also a major hazard or threat during storage failure. Windows Storage Spaces and OpenStack Swift spread the load much broader and as a result are much much faster.
Using Storage Spaces or Swift, it should be cost effective to enable a storage tier at top of rack using two mostly flash based servers. Then a mostly spindle based tier made up of near-line storage for the entire data center. This means that where VMware caps at about 90,000 IOPS per node, a storage spaces or swift system can do 500,000+ IOPs per rack and carry dedup across the wire where VMware doesn't carry it to the next tier. VMware's performance is a dog with fleas because of silly cluster limits imposed on ESXi and Virtual SAN. Azure and OpenStack don't have those silly limits tied to storage. As a result, it scales much further.
Even with the stupid design of VMware vSphere 6, it can still scale to about 6,000,000 IOPs or 7,000,000 if the moon is just right per 64 blades. Storage spaces and swift will scale far past that. In fact.
So, using a SAN from Hitachi, NetApp, EMC, etc... is just a waste of money.