Your question is a tad ambiguous. Do you mean:

1) If you are needing multiple HOSTS to access the same storage that's defined on each host the then in server 2016 it's called Storage Spaces Direct, there is also Starwind Virtual SAN for older server OS's.

You define each HOST with local storage, this 'software gizmo' adds each local storage as one storage system, usually called a VSAN. The total size is the size of ONE of the local storage arrays. The VSAN then mirrors each local storage against each other so that EACH local storage has access to the same VMs resources. The hypervisor referees which hypervisor runs the VM.

2) If you simply want an external SAN for a single Hyper-V host, then simply get one that is Hyper-V compatible, has adequate space and has a fast enough network interface to not choke the host. Dual 1GB NICs (or MORE - and one each, the host and the SAN) that can be teamed on a compatible switch to get maximum throughput would net you the best performance. More disks is better, the more spindles there are the faster it typically can respond.

It's still hardware, but the disk storage is separate from the hypervisor.